Research ArticleVariation in the Permeability of Intact and FracturedRocks due toTransient Disturbances in Axial Stress or Pore Pressure

Sophea Boeut 1 Teppei Oshima2 Yoshiaki Fujii 1 Jun-ichi Kodama1

Daisuke Fukuda 1 Hiroyuki Matsumoto3 Kazumi Uchida3

and Anjula B N Dassanayake 4

1Rock Mechanics Laboratory Graduate School of Engineering Hokkaido University Kita 13 Nishi 8Kita-ku Sapporo Hokkaido 060-8628 Japan2DOWA Metals amp Mining Co Ltd Tokyo Japan3Kushiro Coal Mine Kushiro Japan4University of Moratuwa Moratuwa Sri Lanka

Correspondence should be addressed to Sophea Boeut boeurtsopheagmailcom

Received 8 February 2019 Accepted 21 May 2019 Published 13 June 2019

Academic Editor Sanjay Nimbalkar

Copyright copy 2019 Sophea Boeut et al )is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A persistent increase in the permeability of rock mass caused by transient stress disturbances if present could explain thevariation in the groundwater level in far fields increase in petroleum production caused by earthquakes or artificial vibrations inenhanced oil recovery and induction of earthquakes by seismic waves in intermediate and far fields However it has not beenverified whether the transient stress disturbances induce an increase or decrease in the rock permeability In this study thepermeability values of intact and triaxially fractured Kushiro Cretaceous sandstone and Shikotsu welded tuff were measuredbefore and after transient axial stress or pore pressure disturbances to clarify the effects of transient stress disturbances on rockpermeability According to the experimental results the stress disturbances showed either decreasing or increasing effects on thepermeability depending on the rock type and experimental conditions However when focusing on the fractured rocks rather thanthe intact ones which would be more important in field applications the argillaceous Kushiro Cretaceous sandstone mainlyexhibited decreasing effects and the glassy Shikotsu welded tuff mainly exhibited increasing effects

1 Introduction

Large earthquakes can lead to persistent variation in thegroundwater level in near fields (within fault length) [1 2])is is observed because of the persistent variation in thepermeability of rock mass which is due to the variation instrain this variation is in turn caused by fault movementSuch variations may also occur in an intermediate field (fromone to multiple fault lengths) [3] However it was shown thatthose persistent modifications in the groundwater level mayeven occur in the far field (many fault lengths) up tothousands of kilometers from the epicenter [4 5]

)e persistent variation in the groundwater level in thefar field cannot be explained by the variation in permeabilityassociated with the strain alteration due to the faultmovement this is because the variation in strain in the far

field is transient Manga et al [4] suggested that the per-sistent variation in the groundwater level might rather bedue to a persistent increase in rock mass permeability whichis in turn caused by transient stress disturbances from theseismic waves of earthquakes

A persistent increase in the permeability of rock masscaused by transient stress disturbances if present couldexplain the increase in petroleum production caused byearthquakes or artificial vibrations [6] as that seen in en-hanced oil recovery [7] Manga et al [4] also implied thepossibility that seismic waves induce earthquakes in the in-termediate and far fields Even the decrease in giant (Mge 8)earthquakes in the 1960s and 1990s during which time theUnited States the Union of Soviet Socialist Republics andother countries frequently carried out underground nuclearexplosion tests [8] might be explained by the induction of

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 1312746 16 pageshttpsdoiorg10115520191312746

numerous small earthquakes )ese earthquakes were a resultof the variation in rock mass permeability due to transientstress disturbances which were in turn caused by the seismicwaves of the test explosions

However it has not been verified whether the transientstress disturbances induce an increase or decrease in the rockpermeability (Table 1) In this study the permeability valuesof intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff were measured beforeand after transient axial stress or pore pressure disturbancesto clarify the effects of transient stress disturbances on rockpermeability

It is difficult to compare the results from previous studies(Table 1) because the rock types were different from study tostudy the permeability was measured for only one rockcondition (intact fractured or in situ) and for only one typeof disturbance (pore pressure axial displacement or axialstress) in each study In this research the permeability valuesof both the intact and fractured rock specimens weremeasured and the disturbance types included both transientaxial stress and pore pressure so that the effects of transientstress disturbances on the permeability between rock typesrock conditions and disturbance types could be compared

2 Materials and Methods

21 Rock Samples )e Kushiro Cretaceous sandstone wassampled from the Cretaceous sandstone layer of the KushiroCoal Mine [13] which is located in the eastern region ofHokkaido Japan Methane gas has been extracted from theCretaceous layer underlying the Paleogene coal-bearingformation

)e rock comprises of a matrix of quartz plagioclasesand silt-size smectite (Figure 1 Table 2) and is classified aswacke fine-grained sandstone )e grain sizes of the quartzare between 02 and 04mm and the plagioclase grains areless than 02mm and have an angular to subangular form)e average porosity is 11 (Table 3)

A rock block of Shikotsu welded tuff having a porosity of32 (Table 3) was taken from Sapporo Japan )e glassyrock sample which originated from pyroclastic depositsfrom the eruption of the Shikotsu volcano 40000 years agois predominantly composed of plagioclase hyperstheneaugite hornblende and transparent volcanic glass having afelt-like structure in the matrix )e mineral grain sizes arebetween 03 and 15mm for the plagioclase approximately05mm for the hypersthene 03ndash07mm for the augite and05ndash10mm for the hornblende [14]

22 Sample Preparation and Permeability MeasurementCylindrical specimens (30mm in diameter 60mm inheight) were bored from the 65mm diameter KushiroCretaceous sandstone cores along the vertical drilling axisand from the rock block of the Shikotsu welded tuff along theslowest (167 kms) P-wave velocity direction )e velocitiesin the two other perpendicular directions were 182 kms and211 kms )e specimens were dried at 80degC in an oven forapproximately two days before being vacuum-saturated in

pure water for 3 days Each specimen was connected to a pairof stainless-steel end pieces that had a center hole to allowwater to flow through the specimen A coating of siliconsealant was applied to the lateral surface of each specimen tomaintain the water flow within the specimens A heat-shrinkable tube was used to jacket the specimen with theend pieces to prevent direct contact of the confining fluidwith the specimen Each jacketed specimen was vacuum-saturated again for 24 h and placed in an ultracompacttriaxial cell ([15] Figure 2) Axial stress or pore pressuretransient disturbances were applied to the intact specimensand then to triaxially fractured specimens

For the Kushiro Cretaceous sandstone (Table 4) theconfining pressures were 3 10 or 15MPa )e pore pressurewas 1MPa at the bottom of the specimen and the upper endof the specimen was open to the atmosphere (Figure 2) )eaxial stress disturbances were triangular at 05Hz for 200 s(Figure 3(a)) and the amplitude was up to 11MPa )erectangular disturbances of pore pressure fluctuated between02 and 18MPa A pore pressure (PP) of 1MPa in theconstant hydrostatic stress state was the initial pore pressureand the minimum pore pressure (PP-min) was first manuallyapplied followed by the maximum pore pressure (PP-max))edisturbances had a duration of approximately 200 s withfrequency between 005 and 018Hz under a 10MPa con-fining pressure (Table 4 and Figure 3(b)) Considering the lowpermeability a 10minus5 sminus1 (0036mms) strain-rate-controlledtriaxial compression was applied It should be noted that theaxial stress disturbances for the intact rocks might also havecaused pore pressure disturbances inside the specimens be-cause of the low permeability On the contrary pore pressuredisturbances would not induce axial stress disturbances evenfor intact specimens because the response of the loadingframe was sufficiently rapid

For the Shikotsu welded tuff (Table 5) nearly rectangularaxial stress disturbances were applied with pore pressures of01 and 05MPa and a confining pressure of 5MPa(Figure 4(a)) Axial stress disturbance amplitudes of 0 or8MPa at 005Hz for 200 s were applied (Table 5) )e samepore pressure confining pressure and disturbance fre-quency were used for the rectangular transient pore pressuredisturbances )e applied disturbance amplitudes werebetween 0 and 08MPa)e triaxial compression rate was setat 10minus4 sminus1 (036mms) considering the high permeability

)e axial stress disturbances would not cause porepressure disturbances inside a specimen even for the intactrocks because of their high permeability

)e disturbance frequency was first set at 05Hz for theaxial stress disturbances on the Kushiro Cretaceous sandstonesimulating a moderate earthquake However the frequencyvaried because of the limiting speed for the manual operationof the syringe pump and it was finally set at 005Hz )eresults would have been slightly affected by the differences inthe disturbance wave shapes Furthermore the differences inthe disturbance frequency may have quantitatively affectedthe results However the effects of this difference would notbe sufficient to lead to opposite conclusions

)e permeability values of the intact rock before andafter the transient stress disturbances in the prefailure

2 Advances in Civil Engineering

regime k1 and k2 respectively and those of the fracturedrock before and after the transient stress disturbances in thepostfailure regime k3 and k4 respectively were evaluated bysubstituting the flow rate which was calculated based on thevariations in the water volume in the syringe pump over 24 hfor the Kushiro Cretaceous sandstone (Figure 3) or over 60 sfor the Shikotsu welded tuff (Figure 4) )ese permeabilityvalues were calculated by substituting the flow rate into thefollowing Darcyrsquos equation

k qμA

dp

dx1113888 1113889

minus1

(1)

where k (m2) is the permeability q is the flow rate (m3s) μ isthe fluid viscosity (Pamiddots) A is the cross-sectional area (m2) ofthe specimen and dpdx is the pressure gradient (Pam))eviscosity of water (μ) is 957times10minus4 (Pamiddots) at 295K which isthe air temperature of the testing room that was keptconstant with the aid of an air conditioner

Table 2 Mineral composition of the Kushiro Cretaceous sandstone from XRD analysis

Qz Pl Kf Am Hm Mc Chl SmVery abundant Very abundant Abundant Very little Little Little Little MediumQz quartz Pl plagioclases Kf potash feldspar Am amphibole Hm hematite Mc mica Chl chlorite Sm smectite

Table 3 Physical properties of the rock samples shown as the average value (number of specimens)plusmn standard deviation

PropertiesKushiro Cretaceous sandstone Shikotsu welded tuff

Dry Saturated Dry SaturatedPorosity () 1053 (9)plusmn 243 3165 (18)plusmn 165Density (gcm3) 237 (9)plusmn 002 248 (9)plusmn 002 130 (18)plusmn 001 162 (18)plusmn 002VP (kms) 335 (9)plusmn 014 304 (9)plusmn 016 214 (18)plusmn 007 192 (18)plusmn 014

Table 1 Experimental conditions and effect of stress disturbances on permeability

Experiments Frequency(Hz)

Peakamplitude Disturbances Samples Permeability

response

Elkhoury et al [9] 005 002ndash03MPa Pore pressure Fracturedin situ Berea sandstone Increase

Roberts [10] 25ndash75 03ndash12MPa Axial stress Intact Berea sandstone Increase

Shmonov et al [11] 005ndash20 Strains 10minus4ndash10minus3 Axial stress Intact Limestone basalts gabbroIncrease

(high T130degCndash250degC)Decrease (low T 20degC)

Liu amp Manga [12] 03ndash25 Strain 10minus4 Axialdisplacement Fractured Sandstone Decrease

01mm

(a)

01mm

(b)

Figure 1 Microscopic images of the Kushiro Cretaceous sandstone Qz quartz (ϕle 02ndash04mm) Pl plagioclases (ϕle 02mm) Mx matrix(SmndashIl smectitendashillite (silt-size mineral pieces)) Kf potash feldspar (ϕle 02mm) Bi biotite (ϕle 02ndash05mm) Hb ordinary amphibole(ϕle 015mm) AN andesite (ϕle 02mm) TMS transformed mudstone (ϕle 025mm) Mc mica and Chl chlorite

Advances in Civil Engineering 3

3 Results of the Kushiro Cretaceous Sandstone

31 Axial Stress Disturbances According to the stress-straincurves the Kushiro Cretaceous sandstone showed brittlefailure in all specimens (Figure 5(a)) e maximum stressunder the 10MPa conning pressure was in the range of

90ndash150MPa and slightly increased as the transient stressamplitude increased (Figure 5(b))

e variation in permeability at the time of axial stressdisturbance for some specimens in each hydrostatic stressstate is presented in Figure 6 and the impacts of bothtransient stress disturbance and failure are shown in

Specimen

PC

PP

Platen

Syringe Pump

Loading frame

P1

P2Triaxial cell

PC

A

Stress state

P1

P2

q l

PC

Disturbance

σ

σ

PC

Figure 2 Permeability measurement apparatus

Table 4 Experimental conditions for the Kushiro Cretaceous sandstone

Axial stress disturbances Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

Pp PC σA ΔσA σA-min σA-max Samples Pp PC ΔPP PP-min PP-max fAS-KCS1 3 3 1 2 4 Pp-KCS1

1 10

02 09 11 015AS-KCS2

1 10 10

0 10 10 Pp-KCS2 06 07 13 009AS-KCS3 1 95 105 Pp-KCS3 08 09 17 005AS-KCS4 3 85 115 Pp-KCS4 1 05 15 018AS-KCS5 4 8 12 Pp-KCS5 14 03 17 009AS-KCS6 5 75 125 Pp-KCS6 18 01 19 01AS-KCS7 7 65 135 Pp-KCS7 18 01 19 01AS-KCS8 9 55 145 Pp-KCS8 186 007 193 012AS-KCS9 11 45 155 Pp-KCS9 188 007 195 01AS-KCS10 15 15 1 145 155AS-KCS11 5 125 175PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure f frequency Unit of stresses is in mega Pascal (MPa) and frequency is in hertz (Hz)

k1 k2 k3 k4

σAσ

PC

Disturbance Disturbance

σA-min

σA-max

Time

(a)

k1 k2 k3 k4

σA

Time

PP

PC

σ

Disturbance Disturbance PP-max

PP-min

(b)

Figure 3 Experimental procedure for the Kushiro Cretaceous sandstone (a) Axial stress disturbances (b) pore pressure disturbances

4 Advances in Civil Engineering

Figure 7e permeability of this sandstone increased owingto the failure (observed in the variation in permeability inHold-2 to Hold-3 Figure 6 or k2 to k3 Figure 7) as wasreported for the Kimachi sandstone which is a neogenetuaceous sandstone in Japan [15] is occurred althoughthe axial stress disturbances caused the permeability valuesof the intact rocks (variation in permeability in Hold-1 toHold-2 Figure 6 or k1 to k2 Figure 8(a)) and fractured rocks(variation in permeability in Hold-3 to Hold-4 Figure 6 ork3 to k4 Figure 9(a)) to decrease

e permeability of the intact specimen which is ba-sically shown in Hold-1 and Hold-2 was reduced even withno stress disturbances (Figure 6(a)) and the reduction wasnot aected by the axial stress disturbance amplitude(Figures 6 and 8(a)) However the reduction increased as theconning pressure increased (Figure 8(b)) According to theabove results the permeability reduction of the intact rock

(decrease in permeability fromHold-1 to Hold-2 or k1 to k2Figure 8) could mainly be attributed to consolidation overtime under the conning pressure

e decreased eect on permeability was elucidated forfractured rocks referring to Hold-3 (pre-disturbance) andHold-4 (post-disturbance) (Figure 6) e permeability hadalmost no variation under zero disturbances (Figure 6(a))however at the time of the disturbances the permeabilitydecreased (Figures 6(b)ndash6(d))e reduction from k3 to k4 ofthe fractured rocks (Figure 9(a)) was small at zero stressdisturbance amplitude and it increased with the disturbanceamplitude is decrease in permeability did not depend onthe conning pressure (Figure 9(b)) erefore the abovedescribed usual consolidation would not be a predominantmechanism Instead the stress disturbances may have beenenhanced either by the closure of the rupture planes or bythe production of ne gouge particles (Figure 10(b)) the

Table 5 Experimental condition for the Shikotsu welded tu

Axial stress disturbance Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

PC PP σA ΔσA σA-min σA-max Samples PC PP ΔPP PP-min PP-maxAS-T1

5

05

5

0 5 5Pp-T1

5

05

0 05 05AS-T2 Pp-T2AS-T3 Pp-T3AS-T4

8 1 9Pp-T4

01 045 055AS-T5 Pp-T5AS-T6 Pp-T6AS-T7

010 5 5

Pp-T708 01 09AS-T8 Pp-T8

AS-T9 Pp-T9AS-T10 8 1 9 Pp-T10

01

0 01 01AS-T11 Pp-T11Pp-T12Pp-T13

006 007 013Pp-T14Pp-T15

PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure Unit of stresses is mega Pascal (MPa)

Time

σA

k1 k2 k3 k4

Disturbance Disturbance

10 cycles10 cycles σ

2s4s

8s2s

4s

8s

Residual σA-max

σA-min

PC

(a)

k1 k2 k3 k4

Time

σA

PP

Disturbance Disturbance

10 cycles 10 cyclesσ

Residual

PP-max

PP-min

(b)

Figure 4 Experimental procedure for the Shikotsu welded tu (a) Axial stress disturbances (b) pore pressure disturbances

Advances in Civil Engineering 5

sizes of which varied from 10 microm to 500 microm and they eithercaused clogs or settled at the points of the rupture planes thathave the smallest apertures (Figure 10(c) [9 16 17])

32 Pore Pressure Disturbances Specimens for the porepressure disturbance tests were prepared from another rock

core obtained from a slightly dierent depth All specimensfailed in a brittle manner e maximum stresses were in therange of 70ndash90MPa (Figure 11(a)) and increased slightlywith the pore pressure disturbance amplitude (Figure 11(b))Permeability increased due to failure (k2 to k3) but decreaseddue to pore pressure disturbances (k1 to k2 and k3 to k4)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(a)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(b)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

FracturedDist1 Dist2

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 6 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of axial stressdisturbance for the entire experiment (a) AS-KCS2 (b) AS-KCS5 (c) AS-KCS8 and (d) AS-KCS9 Dist 1 and Dist 2 are the disturbances inprefailure and postfailure

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8 AS-KCS12

AS-KCS9

AS-KCS11AS-KCS10

0

30

60

90

120

150A

xial

stre

ss (M

Pa)

05 1 15 2 250Axial strain ()

(a)

AS-KCS2AS-KCS3AS-KCS4AS-KCS5

AS-KCS6AS-KCS7AS-KCS8AS-KCS9

Axial stress disturbance

r = 035

0

50

100

150

σ max

2 4 6 8 10 120ΔσA (MPa)

(b)

Figure 5 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitudes of the axial stress disturbances (ΔσA) under PC 10MPaof the Kushiro Cretaceous sandstone

6 Advances in Civil Engineering

(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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regime k1 and k2 respectively and those of the fracturedrock before and after the transient stress disturbances in thepostfailure regime k3 and k4 respectively were evaluated bysubstituting the flow rate which was calculated based on thevariations in the water volume in the syringe pump over 24 hfor the Kushiro Cretaceous sandstone (Figure 3) or over 60 sfor the Shikotsu welded tuff (Figure 4) )ese permeabilityvalues were calculated by substituting the flow rate into thefollowing Darcyrsquos equation

k qμA

dp

dx1113888 1113889

minus1

(1)

where k (m2) is the permeability q is the flow rate (m3s) μ isthe fluid viscosity (Pamiddots) A is the cross-sectional area (m2) ofthe specimen and dpdx is the pressure gradient (Pam))eviscosity of water (μ) is 957times10minus4 (Pamiddots) at 295K which isthe air temperature of the testing room that was keptconstant with the aid of an air conditioner

Table 2 Mineral composition of the Kushiro Cretaceous sandstone from XRD analysis

Qz Pl Kf Am Hm Mc Chl SmVery abundant Very abundant Abundant Very little Little Little Little MediumQz quartz Pl plagioclases Kf potash feldspar Am amphibole Hm hematite Mc mica Chl chlorite Sm smectite

Table 3 Physical properties of the rock samples shown as the average value (number of specimens)plusmn standard deviation

PropertiesKushiro Cretaceous sandstone Shikotsu welded tuff

Dry Saturated Dry SaturatedPorosity () 1053 (9)plusmn 243 3165 (18)plusmn 165Density (gcm3) 237 (9)plusmn 002 248 (9)plusmn 002 130 (18)plusmn 001 162 (18)plusmn 002VP (kms) 335 (9)plusmn 014 304 (9)plusmn 016 214 (18)plusmn 007 192 (18)plusmn 014

Table 1 Experimental conditions and effect of stress disturbances on permeability

Experiments Frequency(Hz)

Peakamplitude Disturbances Samples Permeability

response

Elkhoury et al [9] 005 002ndash03MPa Pore pressure Fracturedin situ Berea sandstone Increase

Roberts [10] 25ndash75 03ndash12MPa Axial stress Intact Berea sandstone Increase

Shmonov et al [11] 005ndash20 Strains 10minus4ndash10minus3 Axial stress Intact Limestone basalts gabbroIncrease

(high T130degCndash250degC)Decrease (low T 20degC)

Liu amp Manga [12] 03ndash25 Strain 10minus4 Axialdisplacement Fractured Sandstone Decrease

01mm

(a)

01mm

(b)

Figure 1 Microscopic images of the Kushiro Cretaceous sandstone Qz quartz (ϕle 02ndash04mm) Pl plagioclases (ϕle 02mm) Mx matrix(SmndashIl smectitendashillite (silt-size mineral pieces)) Kf potash feldspar (ϕle 02mm) Bi biotite (ϕle 02ndash05mm) Hb ordinary amphibole(ϕle 015mm) AN andesite (ϕle 02mm) TMS transformed mudstone (ϕle 025mm) Mc mica and Chl chlorite

Advances in Civil Engineering 3

3 Results of the Kushiro Cretaceous Sandstone

31 Axial Stress Disturbances According to the stress-straincurves the Kushiro Cretaceous sandstone showed brittlefailure in all specimens (Figure 5(a)) e maximum stressunder the 10MPa conning pressure was in the range of

90ndash150MPa and slightly increased as the transient stressamplitude increased (Figure 5(b))

e variation in permeability at the time of axial stressdisturbance for some specimens in each hydrostatic stressstate is presented in Figure 6 and the impacts of bothtransient stress disturbance and failure are shown in

Specimen

PC

PP

Platen

Syringe Pump

Loading frame

P1

P2Triaxial cell

PC

A

Stress state

P1

P2

q l

PC

Disturbance

σ

σ

PC

Figure 2 Permeability measurement apparatus

Table 4 Experimental conditions for the Kushiro Cretaceous sandstone

Axial stress disturbances Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

Pp PC σA ΔσA σA-min σA-max Samples Pp PC ΔPP PP-min PP-max fAS-KCS1 3 3 1 2 4 Pp-KCS1

1 10

02 09 11 015AS-KCS2

1 10 10

0 10 10 Pp-KCS2 06 07 13 009AS-KCS3 1 95 105 Pp-KCS3 08 09 17 005AS-KCS4 3 85 115 Pp-KCS4 1 05 15 018AS-KCS5 4 8 12 Pp-KCS5 14 03 17 009AS-KCS6 5 75 125 Pp-KCS6 18 01 19 01AS-KCS7 7 65 135 Pp-KCS7 18 01 19 01AS-KCS8 9 55 145 Pp-KCS8 186 007 193 012AS-KCS9 11 45 155 Pp-KCS9 188 007 195 01AS-KCS10 15 15 1 145 155AS-KCS11 5 125 175PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure f frequency Unit of stresses is in mega Pascal (MPa) and frequency is in hertz (Hz)

k1 k2 k3 k4

σAσ

PC

Disturbance Disturbance

σA-min

σA-max

Time

(a)

k1 k2 k3 k4

σA

Time

PP

PC

σ

Disturbance Disturbance PP-max

PP-min

(b)

Figure 3 Experimental procedure for the Kushiro Cretaceous sandstone (a) Axial stress disturbances (b) pore pressure disturbances

4 Advances in Civil Engineering

Figure 7e permeability of this sandstone increased owingto the failure (observed in the variation in permeability inHold-2 to Hold-3 Figure 6 or k2 to k3 Figure 7) as wasreported for the Kimachi sandstone which is a neogenetuaceous sandstone in Japan [15] is occurred althoughthe axial stress disturbances caused the permeability valuesof the intact rocks (variation in permeability in Hold-1 toHold-2 Figure 6 or k1 to k2 Figure 8(a)) and fractured rocks(variation in permeability in Hold-3 to Hold-4 Figure 6 ork3 to k4 Figure 9(a)) to decrease

e permeability of the intact specimen which is ba-sically shown in Hold-1 and Hold-2 was reduced even withno stress disturbances (Figure 6(a)) and the reduction wasnot aected by the axial stress disturbance amplitude(Figures 6 and 8(a)) However the reduction increased as theconning pressure increased (Figure 8(b)) According to theabove results the permeability reduction of the intact rock

(decrease in permeability fromHold-1 to Hold-2 or k1 to k2Figure 8) could mainly be attributed to consolidation overtime under the conning pressure

e decreased eect on permeability was elucidated forfractured rocks referring to Hold-3 (pre-disturbance) andHold-4 (post-disturbance) (Figure 6) e permeability hadalmost no variation under zero disturbances (Figure 6(a))however at the time of the disturbances the permeabilitydecreased (Figures 6(b)ndash6(d))e reduction from k3 to k4 ofthe fractured rocks (Figure 9(a)) was small at zero stressdisturbance amplitude and it increased with the disturbanceamplitude is decrease in permeability did not depend onthe conning pressure (Figure 9(b)) erefore the abovedescribed usual consolidation would not be a predominantmechanism Instead the stress disturbances may have beenenhanced either by the closure of the rupture planes or bythe production of ne gouge particles (Figure 10(b)) the

Table 5 Experimental condition for the Shikotsu welded tu

Axial stress disturbance Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

PC PP σA ΔσA σA-min σA-max Samples PC PP ΔPP PP-min PP-maxAS-T1

5

05

5

0 5 5Pp-T1

5

05

0 05 05AS-T2 Pp-T2AS-T3 Pp-T3AS-T4

8 1 9Pp-T4

01 045 055AS-T5 Pp-T5AS-T6 Pp-T6AS-T7

010 5 5

Pp-T708 01 09AS-T8 Pp-T8

AS-T9 Pp-T9AS-T10 8 1 9 Pp-T10

01

0 01 01AS-T11 Pp-T11Pp-T12Pp-T13

006 007 013Pp-T14Pp-T15

PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure Unit of stresses is mega Pascal (MPa)

Time

σA

k1 k2 k3 k4

Disturbance Disturbance

10 cycles10 cycles σ

2s4s

8s2s

4s

8s

Residual σA-max

σA-min

PC

(a)

k1 k2 k3 k4

Time

σA

PP

Disturbance Disturbance

10 cycles 10 cyclesσ

Residual

PP-max

PP-min

(b)

Figure 4 Experimental procedure for the Shikotsu welded tu (a) Axial stress disturbances (b) pore pressure disturbances

Advances in Civil Engineering 5

sizes of which varied from 10 microm to 500 microm and they eithercaused clogs or settled at the points of the rupture planes thathave the smallest apertures (Figure 10(c) [9 16 17])

32 Pore Pressure Disturbances Specimens for the porepressure disturbance tests were prepared from another rock

core obtained from a slightly dierent depth All specimensfailed in a brittle manner e maximum stresses were in therange of 70ndash90MPa (Figure 11(a)) and increased slightlywith the pore pressure disturbance amplitude (Figure 11(b))Permeability increased due to failure (k2 to k3) but decreaseddue to pore pressure disturbances (k1 to k2 and k3 to k4)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(a)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(b)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

FracturedDist1 Dist2

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 6 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of axial stressdisturbance for the entire experiment (a) AS-KCS2 (b) AS-KCS5 (c) AS-KCS8 and (d) AS-KCS9 Dist 1 and Dist 2 are the disturbances inprefailure and postfailure

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8 AS-KCS12

AS-KCS9

AS-KCS11AS-KCS10

0

30

60

90

120

150A

xial

stre

ss (M

Pa)

05 1 15 2 250Axial strain ()

(a)

AS-KCS2AS-KCS3AS-KCS4AS-KCS5

AS-KCS6AS-KCS7AS-KCS8AS-KCS9

Axial stress disturbance

r = 035

0

50

100

150

σ max

2 4 6 8 10 120ΔσA (MPa)

(b)

Figure 5 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitudes of the axial stress disturbances (ΔσA) under PC 10MPaof the Kushiro Cretaceous sandstone

6 Advances in Civil Engineering

(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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3 Results of the Kushiro Cretaceous Sandstone

31 Axial Stress Disturbances According to the stress-straincurves the Kushiro Cretaceous sandstone showed brittlefailure in all specimens (Figure 5(a)) e maximum stressunder the 10MPa conning pressure was in the range of

90ndash150MPa and slightly increased as the transient stressamplitude increased (Figure 5(b))

e variation in permeability at the time of axial stressdisturbance for some specimens in each hydrostatic stressstate is presented in Figure 6 and the impacts of bothtransient stress disturbance and failure are shown in

Specimen

PC

PP

Platen

Syringe Pump

Loading frame

P1

P2Triaxial cell

PC

A

Stress state

P1

P2

q l

PC

Disturbance

σ

σ

PC

Figure 2 Permeability measurement apparatus

Table 4 Experimental conditions for the Kushiro Cretaceous sandstone

Axial stress disturbances Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

Pp PC σA ΔσA σA-min σA-max Samples Pp PC ΔPP PP-min PP-max fAS-KCS1 3 3 1 2 4 Pp-KCS1

1 10

02 09 11 015AS-KCS2

1 10 10

0 10 10 Pp-KCS2 06 07 13 009AS-KCS3 1 95 105 Pp-KCS3 08 09 17 005AS-KCS4 3 85 115 Pp-KCS4 1 05 15 018AS-KCS5 4 8 12 Pp-KCS5 14 03 17 009AS-KCS6 5 75 125 Pp-KCS6 18 01 19 01AS-KCS7 7 65 135 Pp-KCS7 18 01 19 01AS-KCS8 9 55 145 Pp-KCS8 186 007 193 012AS-KCS9 11 45 155 Pp-KCS9 188 007 195 01AS-KCS10 15 15 1 145 155AS-KCS11 5 125 175PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure f frequency Unit of stresses is in mega Pascal (MPa) and frequency is in hertz (Hz)

k1 k2 k3 k4

σAσ

PC

Disturbance Disturbance

σA-min

σA-max

Time

(a)

k1 k2 k3 k4

σA

Time

PP

PC

σ

Disturbance Disturbance PP-max

PP-min

(b)

Figure 3 Experimental procedure for the Kushiro Cretaceous sandstone (a) Axial stress disturbances (b) pore pressure disturbances

4 Advances in Civil Engineering

Figure 7e permeability of this sandstone increased owingto the failure (observed in the variation in permeability inHold-2 to Hold-3 Figure 6 or k2 to k3 Figure 7) as wasreported for the Kimachi sandstone which is a neogenetuaceous sandstone in Japan [15] is occurred althoughthe axial stress disturbances caused the permeability valuesof the intact rocks (variation in permeability in Hold-1 toHold-2 Figure 6 or k1 to k2 Figure 8(a)) and fractured rocks(variation in permeability in Hold-3 to Hold-4 Figure 6 ork3 to k4 Figure 9(a)) to decrease

e permeability of the intact specimen which is ba-sically shown in Hold-1 and Hold-2 was reduced even withno stress disturbances (Figure 6(a)) and the reduction wasnot aected by the axial stress disturbance amplitude(Figures 6 and 8(a)) However the reduction increased as theconning pressure increased (Figure 8(b)) According to theabove results the permeability reduction of the intact rock

(decrease in permeability fromHold-1 to Hold-2 or k1 to k2Figure 8) could mainly be attributed to consolidation overtime under the conning pressure

e decreased eect on permeability was elucidated forfractured rocks referring to Hold-3 (pre-disturbance) andHold-4 (post-disturbance) (Figure 6) e permeability hadalmost no variation under zero disturbances (Figure 6(a))however at the time of the disturbances the permeabilitydecreased (Figures 6(b)ndash6(d))e reduction from k3 to k4 ofthe fractured rocks (Figure 9(a)) was small at zero stressdisturbance amplitude and it increased with the disturbanceamplitude is decrease in permeability did not depend onthe conning pressure (Figure 9(b)) erefore the abovedescribed usual consolidation would not be a predominantmechanism Instead the stress disturbances may have beenenhanced either by the closure of the rupture planes or bythe production of ne gouge particles (Figure 10(b)) the

Table 5 Experimental condition for the Shikotsu welded tu

Axial stress disturbance Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

PC PP σA ΔσA σA-min σA-max Samples PC PP ΔPP PP-min PP-maxAS-T1

5

05

5

0 5 5Pp-T1

5

05

0 05 05AS-T2 Pp-T2AS-T3 Pp-T3AS-T4

8 1 9Pp-T4

01 045 055AS-T5 Pp-T5AS-T6 Pp-T6AS-T7

010 5 5

Pp-T708 01 09AS-T8 Pp-T8

AS-T9 Pp-T9AS-T10 8 1 9 Pp-T10

01

0 01 01AS-T11 Pp-T11Pp-T12Pp-T13

006 007 013Pp-T14Pp-T15

PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure Unit of stresses is mega Pascal (MPa)

Time

σA

k1 k2 k3 k4

Disturbance Disturbance

10 cycles10 cycles σ

2s4s

8s2s

4s

8s

Residual σA-max

σA-min

PC

(a)

k1 k2 k3 k4

Time

σA

PP

Disturbance Disturbance

10 cycles 10 cyclesσ

Residual

PP-max

PP-min

(b)

Figure 4 Experimental procedure for the Shikotsu welded tu (a) Axial stress disturbances (b) pore pressure disturbances

Advances in Civil Engineering 5

sizes of which varied from 10 microm to 500 microm and they eithercaused clogs or settled at the points of the rupture planes thathave the smallest apertures (Figure 10(c) [9 16 17])

32 Pore Pressure Disturbances Specimens for the porepressure disturbance tests were prepared from another rock

core obtained from a slightly dierent depth All specimensfailed in a brittle manner e maximum stresses were in therange of 70ndash90MPa (Figure 11(a)) and increased slightlywith the pore pressure disturbance amplitude (Figure 11(b))Permeability increased due to failure (k2 to k3) but decreaseddue to pore pressure disturbances (k1 to k2 and k3 to k4)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(a)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(b)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

FracturedDist1 Dist2

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 6 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of axial stressdisturbance for the entire experiment (a) AS-KCS2 (b) AS-KCS5 (c) AS-KCS8 and (d) AS-KCS9 Dist 1 and Dist 2 are the disturbances inprefailure and postfailure

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8 AS-KCS12

AS-KCS9

AS-KCS11AS-KCS10

0

30

60

90

120

150A

xial

stre

ss (M

Pa)

05 1 15 2 250Axial strain ()

(a)

AS-KCS2AS-KCS3AS-KCS4AS-KCS5

AS-KCS6AS-KCS7AS-KCS8AS-KCS9

Axial stress disturbance

r = 035

0

50

100

150

σ max

2 4 6 8 10 120ΔσA (MPa)

(b)

Figure 5 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitudes of the axial stress disturbances (ΔσA) under PC 10MPaof the Kushiro Cretaceous sandstone

6 Advances in Civil Engineering

(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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Figure 7e permeability of this sandstone increased owingto the failure (observed in the variation in permeability inHold-2 to Hold-3 Figure 6 or k2 to k3 Figure 7) as wasreported for the Kimachi sandstone which is a neogenetuaceous sandstone in Japan [15] is occurred althoughthe axial stress disturbances caused the permeability valuesof the intact rocks (variation in permeability in Hold-1 toHold-2 Figure 6 or k1 to k2 Figure 8(a)) and fractured rocks(variation in permeability in Hold-3 to Hold-4 Figure 6 ork3 to k4 Figure 9(a)) to decrease

e permeability of the intact specimen which is ba-sically shown in Hold-1 and Hold-2 was reduced even withno stress disturbances (Figure 6(a)) and the reduction wasnot aected by the axial stress disturbance amplitude(Figures 6 and 8(a)) However the reduction increased as theconning pressure increased (Figure 8(b)) According to theabove results the permeability reduction of the intact rock

(decrease in permeability fromHold-1 to Hold-2 or k1 to k2Figure 8) could mainly be attributed to consolidation overtime under the conning pressure

e decreased eect on permeability was elucidated forfractured rocks referring to Hold-3 (pre-disturbance) andHold-4 (post-disturbance) (Figure 6) e permeability hadalmost no variation under zero disturbances (Figure 6(a))however at the time of the disturbances the permeabilitydecreased (Figures 6(b)ndash6(d))e reduction from k3 to k4 ofthe fractured rocks (Figure 9(a)) was small at zero stressdisturbance amplitude and it increased with the disturbanceamplitude is decrease in permeability did not depend onthe conning pressure (Figure 9(b)) erefore the abovedescribed usual consolidation would not be a predominantmechanism Instead the stress disturbances may have beenenhanced either by the closure of the rupture planes or bythe production of ne gouge particles (Figure 10(b)) the

Table 5 Experimental condition for the Shikotsu welded tu

Axial stress disturbance Pore pressure disturbances

SamplesConstant

hydrostatic stress Transient axial stress Constant hydrostaticstress Transient pore pressure

PC PP σA ΔσA σA-min σA-max Samples PC PP ΔPP PP-min PP-maxAS-T1

5

05

5

0 5 5Pp-T1

5

05

0 05 05AS-T2 Pp-T2AS-T3 Pp-T3AS-T4

8 1 9Pp-T4

01 045 055AS-T5 Pp-T5AS-T6 Pp-T6AS-T7

010 5 5

Pp-T708 01 09AS-T8 Pp-T8

AS-T9 Pp-T9AS-T10 8 1 9 Pp-T10

01

0 01 01AS-T11 Pp-T11Pp-T12Pp-T13

006 007 013Pp-T14Pp-T15

PC conning pressure PP pore pressure ΔσA axial stress disturbance amplitude ΔPP pore pressure disturbance amplitude PP-min minimum porepressure PP-max maximum pore pressure Unit of stresses is mega Pascal (MPa)

Time

σA

k1 k2 k3 k4

Disturbance Disturbance

10 cycles10 cycles σ

2s4s

8s2s

4s

8s

Residual σA-max

σA-min

PC

(a)

k1 k2 k3 k4

Time

σA

PP

Disturbance Disturbance

10 cycles 10 cyclesσ

Residual

PP-max

PP-min

(b)

Figure 4 Experimental procedure for the Shikotsu welded tu (a) Axial stress disturbances (b) pore pressure disturbances

Advances in Civil Engineering 5

sizes of which varied from 10 microm to 500 microm and they eithercaused clogs or settled at the points of the rupture planes thathave the smallest apertures (Figure 10(c) [9 16 17])

32 Pore Pressure Disturbances Specimens for the porepressure disturbance tests were prepared from another rock

core obtained from a slightly dierent depth All specimensfailed in a brittle manner e maximum stresses were in therange of 70ndash90MPa (Figure 11(a)) and increased slightlywith the pore pressure disturbance amplitude (Figure 11(b))Permeability increased due to failure (k2 to k3) but decreaseddue to pore pressure disturbances (k1 to k2 and k3 to k4)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(a)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(b)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

FracturedDist1 Dist2

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 6 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of axial stressdisturbance for the entire experiment (a) AS-KCS2 (b) AS-KCS5 (c) AS-KCS8 and (d) AS-KCS9 Dist 1 and Dist 2 are the disturbances inprefailure and postfailure

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8 AS-KCS12

AS-KCS9

AS-KCS11AS-KCS10

0

30

60

90

120

150A

xial

stre

ss (M

Pa)

05 1 15 2 250Axial strain ()

(a)

AS-KCS2AS-KCS3AS-KCS4AS-KCS5

AS-KCS6AS-KCS7AS-KCS8AS-KCS9

Axial stress disturbance

r = 035

0

50

100

150

σ max

2 4 6 8 10 120ΔσA (MPa)

(b)

Figure 5 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitudes of the axial stress disturbances (ΔσA) under PC 10MPaof the Kushiro Cretaceous sandstone

6 Advances in Civil Engineering

(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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sizes of which varied from 10 microm to 500 microm and they eithercaused clogs or settled at the points of the rupture planes thathave the smallest apertures (Figure 10(c) [9 16 17])

32 Pore Pressure Disturbances Specimens for the porepressure disturbance tests were prepared from another rock

core obtained from a slightly dierent depth All specimensfailed in a brittle manner e maximum stresses were in therange of 70ndash90MPa (Figure 11(a)) and increased slightlywith the pore pressure disturbance amplitude (Figure 11(b))Permeability increased due to failure (k2 to k3) but decreaseddue to pore pressure disturbances (k1 to k2 and k3 to k4)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(a)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(b)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

FracturedDist1 Dist2

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 6 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of axial stressdisturbance for the entire experiment (a) AS-KCS2 (b) AS-KCS5 (c) AS-KCS8 and (d) AS-KCS9 Dist 1 and Dist 2 are the disturbances inprefailure and postfailure

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8 AS-KCS12

AS-KCS9

AS-KCS11AS-KCS10

0

30

60

90

120

150A

xial

stre

ss (M

Pa)

05 1 15 2 250Axial strain ()

(a)

AS-KCS2AS-KCS3AS-KCS4AS-KCS5

AS-KCS6AS-KCS7AS-KCS8AS-KCS9

Axial stress disturbance

r = 035

0

50

100

150

σ max

2 4 6 8 10 120ΔσA (MPa)

(b)

Figure 5 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitudes of the axial stress disturbances (ΔσA) under PC 10MPaof the Kushiro Cretaceous sandstone

6 Advances in Civil Engineering

(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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(Figures 12 and 13) e y-intercept of Figure 14(a) showsthe reduction in the intact rock permeability (k1 to k2) at zerodisturbance is would imply the eect of consolidationover time e reduction decreased as the pore pressuredisturbance amplitudes increased Even for a specimen k2was larger than k1 under larger pore pressure disturbances(Figures 12(c) and 14(a)) is increase in the permeabilitycould be induced by the formation of microfractures due tothe pore pressure disturbances However as shown inFigure 6(b) the strength was not reduced with pore pressuredisturbances and hence the formation of microfractures

would not be the main mechanism e removal of thebarriers that clogged the existing pathways [4 18 19] wouldbe a preferable explanation for this nding

e reduction in permeability due to pore pressuredisturbances for the fractured specimens (in postfailureHold-3 to Hold-4 in Figure 12 or k3 to k4 in Figure 14(b))was not very large at zero disturbances and slightly increasedas the pore pressure disturbance amplitude increased al-though the r value (the coecient of correlation) is low emechanisms would be similar to those of the fractured rockswith axial stress disturbances

r = 001

Decreased amount

Outlier

Pc = 10 (MPa)

0

05

1

15

2

k 2k

1

8 1062 40∆σA (MPa)

(a)

r = minus 099

Decreased amount

ΔσA = 1 (MPa)

0

05

1

15

2

k 2k

1

10 155PC (MPa)

(b)

Figure 8 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the intact rocks e outlier data pointwas ignored for the regression analysis

Fractured

Disturbed

Disturbed

AS-KCS1AS-KCS2AS-KCS3AS-KCS4

AS-KCS5AS-KCS6AS-KCS7AS-KCS8

AS-KCS9AS-KCS10AS-KCS11

k1 k2 k3 k4

10ndash19

10ndash18

Perm

eabi

lity

(m2 )

Figure 7 Variation in permeability in each hydrostatic stress state at the time of axial stress disturbances and triaxial compression

Advances in Civil Engineering 7

4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

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4 Result of the Shikotsu Welded Tuff

e Shikotsu welded tu specimens failed in a ductile mannerwith slight stress drops (Figures 15(a) and 16(a))emaximumstress was aected by neither the axial stress (Figure 15(b)) northe pore pressure disturbances (Figure 16(b))

41 Axial Stress Disturbances e axial stress disturbancetests were conducted under 05 (Figure 17) or 01MPa(Figure 18) in pore pressureWith the application of 05MPain pore pressure the permeability showed an increase for theintact rocks (Figure 17(b)) is would occur because of thecleaning of the pore throats and the micropathways by therapid water ow [12 18 19] e increased permeability wasnot aected by the disturbance amplitude (Figure 17(b))e permeability decreased from k2 to k3 due to rock failure

(Figure 17(a)) and this result is the same as those presentedby Alam et al [15] for the same rock type is reduction inpermeability may be due to the crushing of the matrix thatconsists of volcanic glass (Figure 19(a)) e permeabilityfurther decreased from k3 to k4 at zero disturbances(Figure 17(c)) is would be due to the closure of therupture planes and the clogging of the smallest apertures bysome ne particles over time ese decreases were reducedas the disturbance amplitude increased (Figure 17(c)) iswould be due to the generation and unclogging of themicrofracture paths (Figure 19(b)) [4 12 20 21]

Under a pore pressure of 01MPa the permeability de-creased from k1 to k2 and k3 (Figure 18(a)) e reducedpermeability from k1 to k2 (Figure 18(b)) was almost constantwith the axial stress disturbance amplitudes for the intactrocksismay suggest that the rock was slightly consolidatedover time and that the water ow was not suciently rapid to

Wat

er fl

ow d

irect

ion

(a)

300microm

(b)

Axial disturbance

Axial disturbance

New clogging

Uncloggingwith shaking

Flow

Flow

Seal

ed

Seal

ed

(c)

Figure 10 A specimen after an experiment (Pp-KCS3) (a) specimen showing the rupture plane (b) gouge along the rupture plane and themicroscopic image of the particles along the rupture plane and (c) clogging and unclogging of an aperture by particles [12]

r = minus070

Pc = 10 (MPa)

Decreased amount

Decrease

Outlier

2 4 6 8 100∆σA (MPa)

0

05

1

15

2

k 4k

3

(a)

r = minus 028

ΔσA = 1 (MPa)

Decreased amount

10 155PC (MPa)

0

05

1

15

2

k 4k

3

(b)

Figure 9 Permeability ratio vs (a) axial stress disturbance amplitude and (b) conning pressure of the fractured rocks

8 Advances in Civil Engineering

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

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RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

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Active and Passive Electronic Components

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Shock and Vibration

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Submit your manuscripts atwwwhindawicom

clean up the pore throats e permeability decreased for thefractured rocks at zero stress disturbances (k3 to k4Figure 18(c)) However the reduction decreased as the stress

disturbances increased (Figure 18(c)) which was probablydue to mechanisms similar to those of the 05MPa case(Figure 17(c))

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

9616 24 32 40 48 56 64 72 80 8880Time (h)

(a)

Dist1

Hold-1

Dist2Fractured

Hold-2 Hold-3 Hold-4

8 16 240 40 48 56 64 72 80 88 9632Time (h)

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

(b)

Hold-1

Dist1

Hold-2

Dist2Fractured

Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(c)

Dist1 Dist2Fractured

Hold-1 Hold-2 Hold-3 Hold-4

10ndash21

10ndash20

10ndash19

10ndash18

10ndash17

Perm

eabi

lity

(m2 )

8 16 24 32 40 48 56 64 72 80 88 960Time (h)

(d)

Figure 12 Variation in permeability in each hydrostatic stress state (Hold-1 Hold-2 Hold-3 and Hold-4) at the time of transient porestress disturbances for the whole experiment (a) Pp-KCS1 (b) Pp-KCS4 (c) Pp-KCS6 and (d) Pp-KCS7 Dist 1 and Dist 2 are thedisturbances in prefailure and postfailure respectively

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

Axi

al st

ress

(MPa

)

0 1 15 205Axial strain ()

(a)

r = 038

Pore pressure disturbance

Pp-KCS1Pp-KCS2Pp-KCS3

Pp-KCS4Pp-KCS5Pp-KCS6

Pp-KCS7Pp-KCS8Pp-KCS9

0

20

40

60

80

100

σ max

05 1 15 20ΔPP (MPa)

(b)

Figure 11 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitudes of the pore pressure disturbances (ΔPP) of the KushiroCretaceous sandstone

Advances in Civil Engineering 9

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

r = 041

03 06 09 12 15 180∆PP (MPa)

0

05

1

15

2

k 2k

1

(a)

r = minus 017

03 06 09 12 15 180ΔPP (MPa)

0

05

1

15

2k 4

k3

(b)

Figure 14 Eect of pore pressure disturbances on the permeability ratio of the Kushiro Cretaceous sandstone (a) intact rocks and (b)fractured rocks

Disturbed Disturbed

Fractured

Pp-KCS1Pp-KCS2Pp-KCS3Pp-KCS4

Pp-KCS5Pp-KCS6Pp-KCS7

Pp-KCS7Pp-KCS8Pp-KCS9

10ndash20

10ndash19

10ndash18

k1 k2 k3 k4

Perm

eabi

lity

(m2 )

Figure 13 Permeability variation due to pore pressure disturbances and triaxial compression under PC 10MPa

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T9

AS-T11AS-T10

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

AS-T1AS-T2AS-T3AS-T4

AS-T5AS-T6AS-T7AS-T8

AS-T10AS-T11

AS-T9

0

10

20

30

σ max

2 4 6 80ΔσA (MPa)

r = 015

(b)

Figure 15 (a) Stress-strain curves and (b) maximum stress (σmax) vs amplitude of the axial stress disturbances (ΔσA) of the Shikotsu weldedtu

10 Advances in Civil Engineering

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T9Pp-T10

Pp-T6Pp-T7Pp-T8

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

0

10

20

30

Axi

al st

ress

(MPa

)

05 1 15 2 250Axial strain ()

(a)

Pp-T1Pp-T2Pp-T3Pp-T4Pp-T5

Pp-T6Pp-T7

Pp-T9Pp-T8

Pp-T10

Pp-T11Pp-T12Pp-T13Pp-T14Pp-T15

Pore pressure disturbance

0

10

20

30

σ max

02 04 06 080ΔPP (MPa)

r = 01

(b)

Figure 16 (a) Stress-strain curves and (b) maximum stress (σmax) vs the amplitude of the pore pressure disturbance (ΔPP) of the Shikotsuwelded tu

AS-T4AS-T5AS-T6

AS-T1AS-T2AS-T3

Disturbed

Fractured

Disturbed

3 times 10ndash16

10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 028

08

09

1

11

12

k 2k

1

2 4 6 80ΔσA (MPa)

(b)

r = 088

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 17 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 05MPa) due totransient axial stress disturbances and triaxial compression of the Shikotsu welded tu

AS-T10AS-T11

AS-T7AS-T8AS-T9

Disturbed

Fractured

Disturbed10ndash15

3 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 048

2 4 6 80∆σA (MPa)

08

09

1

11

12

k 2k

1

(b)

r = 097

08

09

1

11

12

k 4k

3

2 4 6 80ΔσA (MPa)

(c)

Figure 18 Variation in permeability (a) and permeability ratios of the intact rocks (b) and fractured rocks (c) (PP 01MPa) due totransient axial stress disturbances and the triaxial compression of the Shikotsu welded tu

Advances in Civil Engineering 11

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

42 Pore Pressure Disturbances )e pore pressure distur-bances that were performed under 05MPa in pore pressure(Figure 20) exhibited results that were similar to those of theaxial stress disturbance

)e results under 01MPa in pore pressure (Figure 21)were also similar to those of the axial stress disturbancesHowever the effects of the disturbances were not clearbecause the amplitude of the pore pressure disturbances at01MPa in pore pressure was just 006MPa )e resultsbasically showed a good repeatability of the tests except for

the reduction of the permeability due to rock failure whichvaried from specimen to specimen

)e k2k1 ratio with zero disturbances was found to be lessthan one at 01MPa in pore pressure and greater than one at05MPa in pore pressure (Figure 22(a)) )is is the same resultthat was found for the axial stress disturbances and wouldindicate that for the intact rocks a higher pore pressurepromoted a more rapid flow that cleaned up the trappedparticles in the pore throats [10 22ndash25] Fractured rocks ex-perienced a greater reduction in permeability under the lower

Main fracture

Crashed zone

Secondary fracture

Raw 1mm 1mm

1mm

(a)

Raw Processed Magnified

Main fracture

1mm 1mm

Flow pathways

(b)

Figure 19 Images of blue resin impregnated thin-section samples after the tests under (a) ΔσA 8MPa PC 5MPa PP 05MPa and (b)ΔPP 08MPa PC 5MPa PP 05MPa Left original images middle processed images to emphasize the blue resin and right magnifiedimages

12 Advances in Civil Engineering

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

pore pressure (Figure 22(b)) which may suggest that moreparticles were accumulated owing to the lower water ow

5 Summary of the Results and Discussion

e eects of transient axial stress disturbances and porepressure disturbances on the permeability values of Kushiro

Cretaceous sandstone and Shikotsu welded tu were in-vestigated under various disturbance amplitudese resultsare summarized as follows

e permeability of the Kushiro Cretaceous sandstone(Table 6) decreased at zero stress disturbances For the intactrocks the permeability reduction became larger as theconning pressure increased but this was not exhibited by

Disturbed

Fractured

Disturbed

Pp-T1Pp-T2Pp-T3

Pp-T4Pp-T5Pp-T6

Pp-T7Pp-T8Pp-T9

3 times 10ndash16

10ndash15Pe

rmea

bilit

y (m

2 )

k1 k2 k3 k4

(a)

r = 065

08

09

1

11

12

k 2k

1

02 04 06 080ΔPp (MPa)

(b)

r = 085

08

09

1

11

12

k 4k

3

02 04 06 080ΔPp (MPa)

(c)

Figure 20 Variation in permeability (a) and permeability ratios of the intact rocks (b) or fractured rocks (c) (PP 05MPa) due to transientpore pressure disturbances and triaxial compression of the Shikotsu welded tu

Pp-T10Pp-T11Pp-T12

Pp-T13Pp-T14Pp-T15

Disturbed

Fractured

Disturbed10ndash15

2 times 10ndash16

2 times 10ndash15

Perm

eabi

lity

(m2 )

k1 k2 k3 k4

(a)

r = 064

08

09

1

11

12

k 2k

1

003 0060ΔPp (MPa)

(b)

r = 037

08

09

1

11

12

k 4k

3

003 0060ΔPp (MPa)

(c)

Figure 21 (a) Variation in permeability and permeability ratios of the intact rocks (b) and the fractured rocks (c) due to transient porepressure disturbances and triaxial compression of the Shikotsu welded tu (PP 01MPa)

r = 095

08

09

1

11

12

k 2k

1

0201 04 0503Pp (MPa)

(a)

r = 095

08

09

1

11

12

k 4k

3

02 03 04 0501Pp (MPa)

(b)

Figure 22 Eect of pore pressure on permeability ratios without stress disturbances (a) Intact (b) fractured

Advances in Civil Engineering 13

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

the fractured rocks In terms of the axial stress disturbanceeffects the permeability was kept almost constant with thedisturbance amplitude for the intact rocks )e reductionsbecame larger as the disturbance amplitudes increased forthe fractured rocks Regarding the pore pressure distur-bances the reductions in permeability of the intact rocksdecreased as the pore pressure disturbances increasedwhereas the reductions increased as the disturbance am-plitudes increased for the fractured rocks

For the case of the Shikotsu welded tuff (Table 7) vir-tually the same results were obtained for both the axial stressand pore pressure disturbances )e permeability values ofthe intact rocks under 05MPa in pore pressure increased atzero stress disturbances )ey decreased under 01MPa inpore pressure with no stress disturbances )e permeability(increase or decrease) was not affected by the disturbanceamplitude)e permeability of the fractured rocks decreasedat zero stress disturbances and the reductions in perme-ability decreased as the disturbance amplitudes increasedand a permeability increase was even observed in some cases

)ese results suggest that the permeability basicallyshows an initial decrease over time because the permeabilitymeasurements were not carried out after a sufficiently longtime for the convergence of the consolidation Howeverafter the initial decrease the stress disturbances wouldbasically cause an increase in the permeability If the rockcontains a considerable amount of clay minerals the in-creasing effect may be offset by a decrease in permeabilitydue to enhanced consolidation caused by the stress dis-turbance )e consolidation effect was relatively stronger inthe fractured rocks)is would happen because of the plastic

and viscous deformations along with the elastic de-formations of themineral particles on and near the rupturedsurface

)e increasing effect of the pore pressure disturbanceswas so strong that even the permeability of the intactKushiro Cretaceous sandstone increased as the disturbanceamplitude increased )is would occur because the porepressure increases isotropically enlarging the water flowpath to remove particles whereas the axial stress distur-bances act only in the axial direction

Considering that the effects of transient stress distur-bances of rockmasses would be different from those of intactrocks but not so significantly different from those of frac-tured rocks and considering that similar effects are likely tooccur for similar rock types it is expected that the per-meability of rockmass consisting of argillaceousglassy rocksmay decreaseincrease owing to transient stressdisturbances

6 Concluding Remarks

To clarify the effects of transient stress disturbances on therock permeability permeability measurements were carriedout on intact and triaxially fractured Kushiro Cretaceoussandstone and Shikotsu welded tuff before and after axialstress or pore pressure transient disturbances According tothe experimental results the stress disturbances showedeither decreasing or increasing effects on the permeabilitydepending on the rock type and experimental conditions

)e permeability of the Kushiro Cretaceous sandstonedecreased at zero stress disturbances For the intact rocks

Table 6 Summary of the variations in permeability of the Kushiro Cretaceous sandstone

Disturbances Intact Fractured

Axial stress

k 2k

1ΔσA

Consolidation

1

k 2k

1

ΔPP

Unclogging

Consolidation

1

Pore pressure

1

∆σA or ∆PP

Closure of rupture planeClogging

k 4k

3

14 Advances in Civil Engineering

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

the permeability was kept almost constant with the dis-turbance amplitude For the fractured rocks the reductionsbecame larger as the disturbance amplitudes increasedRegarding the pore pressure disturbances the reductions inpermeability of the intact rocks decreased as the porepressure disturbances increased whereas the reductionsincreased as the disturbance amplitudes increased for thefractured rocks

For the Shikotsu welded tuff virtually the same resultswere obtained for both the axial stress and pore pressuredisturbances )ere were negligible effects of stress distur-bances for the intact rocks )e permeability of the fracturedrocks decreased at zero stress disturbances and the re-ductions in permeability decreased as the disturbance am-plitudes increased and a permeability increase was evenobserved in some cases

When focusing on the fractured rocks rather than theintact rocks which would be more important in field ap-plications the argillaceous Kushiro Cretaceous sandstonemainly exhibited decreasing effects In contrast the glassyShikotsu welded tuff mainly exhibited increasing effects

)e permeability variations due to transient stress dis-turbances have already been used as a seismic wave-enhanced oil recovery (EOR) technique in which an in-crease in permeability due to the movement of the entrappedfluid in the reservoir [6] is expected An increase in thepermeability may encourage its future utilization to enhancenatural gas recovery to prevent large earthquakes by in-ducing a large number of small earthquakes [4 8 17] and toreroute an underground water flow for various purposes Adecrease in the permeability could be used in the future to

help seal rock caverns and to reroute an underground waterflow for various purposes

Further experiments on different rock types undervarious conditions along with investigations of the mech-anisms of the variations in permeability will assist theclarification of the effects of transient stress disturbances)e persistency of the variations in permeability amongother aspects should also be investigated in the future

Data Availability

)e data used in this study are available from the corre-sponding author upon request

Conflicts of Interest

)e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

)is research was supported by the Japan InternationalCorporation Agency (JICA) under the AUNSEED-Netprogram (J16-10145)

References

[1] C Wang and Y Chia ldquoMechanism of water level changesduring earthquakes near field versus intermediate fieldrdquoGeophysical Research Letters vol 35 no 12 2008

[2] Y Orihara M Kamogawa and T Nagao ldquoPreseismic changesof the level and temperature of confined groundwater related

Table 7 Summary of the variations in permeability of the Shikotsu welded tuff

Disturbances Intact Fractured

Axial stress

k 2k

1∆σA

1

Cleaning

Clogging 01 MPa

05 MPa

k 2k

1

∆PP

1

Cleaning05 MPa

Pore pressure k 4k

3

∆σA or ∆PP

Closure of rupture planeClogging

1

New microcracksUnclogging

Advances in Civil Engineering 15

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

to the 2011 Tohoku earthquakerdquo Scientific Reports vol 4no 1 p 6907 2014

[3] Y Fujii Y Ichihara H Matsumoto J Kodama D Fukudaand A B Dassanayake ldquoWater drainage from Kushiro coalmine decreased on the day of all M ge 75 earthquakes andincreased thereafterrdquo Scientific Reports vol 8 article 164722018

[4] M Manga I Beresnev E E Brodsky et al ldquoChanges inpermeability caused by transient stresses field observationsexperiments andmechanismsrdquo Reviews of Geophysics vol 502012

[5] M Manga and C Wang ldquo412 Earthquake hydrologyrdquoTreatise on Geophysicspp 305ndash328 Elsevier Oxford UK 2ndedition 2015

[6] S R Pride E G Flekkoslashy and O Aursjoslash ldquoSeismic stimulationfor enhanced oil recoveryrdquo Geophysics vol 73 no 5pp O23ndashO35 2008

[7] I A Beresnev R D Vigil W Li et al ldquoElastic waves pushorganic fluids from reservoir rockrdquo Geophysical ResearchLetters vol 32 no 13 2005

[8] Y Fujii M Sheshpari J-i Kodama D Fukuda andA Dassanayake ldquoPrevention of catastrophic volcanic erup-tions large earthquakes underneath big cities and giantearthquakes at subduction zonesrdquo Sustainability vol 10no 6 p 1908 2018

[9] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoLaboratory observations of permeability enhancement byfluid pressure oscillation of in situ fractured rockrdquo Journal ofGeophysical Research Solid Earth vol 116 no B2 2011

[10] P M Roberts ldquoLaboratory observations of altered porousfluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulationrdquo Acoustical Physicsvol 51 no S1 pp S140ndashS148 2005

[11] V M Shmonov V M Vitovtova and A V ZharikovldquoExperimental study of seismic oscillation effect on rockpermeability under high temperature and pressurerdquo In-ternational Journal of Rock Mechanics and Mining Sciencesvol 36 no 3 pp 405ndash412 1999

[12] W Liu and M Manga ldquoChanges in permeability caused bydynamic stresses in fractured sandstonerdquo Geophysical Re-search Letters vol 36 no 20 2009

[13] Y Fujii Y Ishijima Y Ichihara et al ldquoMechanical propertiesof abandoned and closed roadways in the Kushiro Coal MineJapanrdquo International Journal of Rock Mechanics and MiningSciences vol 48 no 4 pp 585ndash596 2011

[14] S Doi ldquoPetrological and petrochemical studies of weldedtuffrdquo Reports of the Geological Survey of Japan vol 29pp 30ndash103 1963

[15] A Alam Y Fujii D Fukuda and M Niioka ldquoTemperature-confining pressure coupling effects on the permeability ofthree rock types under triaxial compressionrdquo Rock Engi-neering and Rock Mechanics Structures in and on RockMasses pp 131ndash136 2014

[16] J Bear Hydraulics of Groundwater McGraw-Hill Series inWater Resources and Environmental Engineering vol 463McGraw-Hill New York NY USA 1979

[17] C Wang and M Manga Earthquakes and Water SpringerBerlin Germany 2009

[18] J E Elkhoury E E Brodsky and D C Agnew ldquoSeismicwaves increase permeabilityrdquo Nature vol 441 no 7097pp 1135ndash1138 2006

[19] I Beresnev W Gaul and R D Vigil ldquoDirect pore-levelobservation of permeability increase in two-phase flow byshakingrdquo Geophysical Research Letters vol 38 2011

[20] R Bai and C Tien ldquoParticle detachment in deep bed filtra-tionrdquo Journal of Colloid and Interface Science vol 186 no 2pp 307ndash317 1997

[21] J Bergendahl and D Grasso ldquoPrediction of colloid de-tachment in a model porous media hydrodynamicsrdquoChemical Engineering Science vol 55 no 9 pp 1523ndash15322000

[22] J E Elkhoury A Niemeijer E E Brodsky and C MaroneldquoDynamic stress stimulates flow in fractures laboratory ob-servations of permeability enhancementrdquo Journal of Geo-physical Research vol 115 2010

[23] E E Brodsky E Roeloffs D Woodcock I Gall andMManga ldquoAmechanism for sustained groundwater pressurechanges induced by distant earthquakesrdquo Journal of Geo-physical Research Solid Earth vol 108 no B8 2003

[24] T Candela E E Brodsky C Marone and D ElsworthldquoLaboratory evidence for particle mobilization as a mecha-nism for permeability enhancement via dynamic stressingrdquoEarth and Planetary Science Letters vol 392 pp 279ndash2912014

[25] T Candela E E Brodsky C Marone and D Elsworth ldquoFlowrate dictates permeability enhancement during fluid pressureoscillations in laboratory experimentsrdquo Journal of GeophysicalResearch Solid Earth vol 120 no 4 pp 2037ndash2055 2015

16 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom