Curs Iit Partea 1
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- CURS -
MASTER INGINERIA INFRASTRUCTURII
TRANSPORTURILOR
UNIVERSITATEA TEHNICĂ DIN CLUJ NAPOCA
FACULTATEA DE CONSTRUCȚII
“MECANICA AVANSATA A PAMANTULUI”
Prof.Dr.Ing. Augustin Popa
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MECANICA PAMANTULUI
1.STRUCTURA PAMANTULUI
1.1.Pamanturi necoezive
1.1.1.Structura granulara (sedimentare)
Fig.1.1.Formarea structurii granulare Fig.1.2.Pamantul – sistem trifazic
minmax
max
ee
eeID
p
s
Ve
V
- Pentru starea cea mai afanata
- Pentru starea cea mai indesata
maxe e
mine e
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• Pamanturi cuartoase : forma alungita (bastoane) sau sferica
• Pot fi indentificate urmatoarele tipuri de contacte intre particulele minerale.
• L-L –contacte intre particule cu suprafata mare
• L-S-L –contacte intre particule cu suprafata mica
• L-S-V –contacte passive
Fig.1.3 Tipuri de contacte intre particulele minerale
Fig.1.4 Forma particulei minerale
1.1.Pamanturi necoezive
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• 1.2.Pamanturi coezive
Fig.1.5.Fortele de legatura intre particulele fine
• Grosimea peliculei de apa (dipoli) fixata pe suprafata particulei argiloase
depinde de suprafata specifica a particulei: montmorillonit: 1000 mp/g ; illit
100 mp/g ; caolinit 10mp/g,
• nisip fin (d=0.1mm): 0.03/g
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• Functie de predominarea fortelor de atractie si respingere, particulele
argiloase au tendinta de a se uni in conglomerate care sedimenteaza.
• a). Ape dulci (concentratie de saruri redusa)- fortele predominante de
respingere (-φ), particulele sedimenteaza individual- contacte fata-fata
Fig.1.6 Structura de tip fagure
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• b).Ape sarate –fortele predominante de atractie (+φ)
Fig.1.7. Structura de tip flocular
• c).Structura mixta- P+H+PF (<0.05mm)
Fig.1.8.Structura pamanturilor fine
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Pamanturile argiloase -forma disc (a) , batoane (bete) (b)
Fig.1.9 Forma particulei argiloase
2.COMPOZITIA GRANULOMETRICA
Cernere d mm
Sedimentare d mm
Fig.2.1.Analiza granulometrica
0.063
0.063
Continutul fractiunilor granulometrice
exprimate in [%] din greutatea totala
a materialului uscat reprezinta
compozitia granulometrica.
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2.1.Clasificare Tabelul 1- Fractiuni granulometrice
Fractiuni ale
pamantului
Subdiviziuni Simboluri Marimea particulelor
( mm )
Pamant foarte
grosier
Blocuri mari Lbo >630
Blocuri Bo >200 pana la 630
Bolovanis Co >63 pana la 200
Pamant grosier Pietris Gr >2.0 pana la 63
Pietris mare CGr >20 pana la 63
Pietris mijlociu MGr >6.3 pana la 20
Pietris mic FGr >2.0 pana la 6.3
Nisip Sa >0.063 pana la 2.0
Nisip mare CSa >0.63 pana la 0.2
Nisip mijlociu MSa >0. 2 pana la 0.63
Nisip fin FSa >0.063 pana la 0.2
Pamant fin Praf Si >0.002 pana la 0.063
Praf mare CSi >0.02 pana la 0.063
Praf mijlociu MSi >0.0063 pana la 0.02
Praf fin FSi >0.002 pana la 0.0063
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• 2.2.Paramentri
• Rezultatul analizei granulometrice se poate exprima grafic in mai multe
forme dintre care cea mai raspandita este curba granulometrica.
• Curba granulometrica – d10 “diametru efectiv”; d30, d50,d60.
Fig.2.2.Curba granulometrica
10
60
d
dcu
6010
2
30
dd
dcc
Forma curbei granulometrice poate fi caracterizata prin:
- coeficient de neuniformitate
- coeficient de curbura
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Curba granulometrica a PIETREI SPARTE
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• Daca a).Cu>6 si 1<Cc<3 – pamantul are o buna gradatie (usor compactabil)
b).alte valori - pamantul are o gradatie pe domeniu mic
c).lipsa unor fractiuni granulometrice – gradatie intermitenta
Fig.2.3.Curba granulometrica pentru tipuri de pamanturi
Important pentru lucrari de umplutura ---NU ---200mm>10%; procentaj particule ≤ 0.063mm >10-15%;
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Materiale pentru TERASAMENTE
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Materiale pentru TERASAMENTE
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Clasificarea pamanturilor pentru constructia TERASAMENTELOR
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Clasificarea pamanturilor GELIVE
Pentru executia straturilor de imbunatatire se utilizeaza urm. AGREGATE:
- Piatra sparta 40-80 mm
- Split 16-25 mm pentru impanarea la partea superioara a stratului de blocaj cu
stratul de piatra sparta
- Nisip grauntos sau savura 0-7 mm ca material de protectie a geotextilului
1. Pentru stratul de blocaj din piatra
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2. Pentru stratul de piatra sparta
- Piatra sparta 0-63 mm, in stratul de imbunatatire
3. Pentru stratul de balast
- Balast 0-63 mm, in stratul cu geogrile
Agregatele trebuie sa provina din roci stabile, adica nealterabile la aer, apa
sau inghet. Se interzice folosirea agregatelor provenite din roci feldspatice sau
sistoase
Piatra sparta utilizata va fi un material format din fragmente de roca
unghiulare obtinute prin concasarea mecanica a urmatoarelor tipuri de roci
provenite din cariere cu depozite de piatra nedeteriorate, bine consolidate:
granit si alte roci vulcanice similare, cu structura larg cristalizata, calcar
dolomitic, gresie, cuartit metamorfic masiv sau alte roci similare
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Agregatele folosite la realizarea straturilor de imbunatatire trebuie sa
indeplineasca conditiile de admisibilitate prezentate in tabelele urmatoare:
NISIP - conditiile de admisibilitate conform SR 662:2002
BALAST - conditiile de admisibilitate pentru fundatii conform SR 662:2002
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PIATRA SPARTA – Conditii de admisibilitate conform SR 667:2001
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BALAST– Granulozitate
Agregatele folosite la realizarea straturilor de imbunatatire trebuie sa
indeplineasca conditiile considerate in Proiectul tehnic.
Ex:
Balastul din stratul de imnunatire
-modul de deformatie liniara E=45000kn
-unghi de frecare interna φ=37◦
-greutate volumica ᵞ=22 kN/mc
Piatra sparta din stratul de imnunatire
-modul de deformatie liniara E=55000kn
-unghi de frecare interna φ=38◦
-greutate volumica ᵞ=23 kN/mc
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PIATRA SPARTA – Conditii de admisibilitate
PIATRA SPARTA – Granulozitate
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3.COMPRESIBILITATEA
• Incarcarea transmisa de fundatie pamantului provoaca in zona de sub talpa fundatiei o stare de tensiuni insotita de o stare de deformatii.
Deformabilitatea pamanturilor este produsa de: - reducerea porozitatii:
-eliminarea apei din pori
-eliminare gaze din pori
Fig.3.1.Compresibilitatea pamantului
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• Relatia dintre tensiuni si deformatii “legea constitutiva a materialului”
Legea lui Hooke:
E- modulul de elasticitate longitudinala (modulul lui Young)
- deformatia liniara specifica
Fig.3.2. Diagrama σ - ε
E
dE tg
d
)(h
h
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• 3.2.Incercari de compresibilitate
3.2.1.Incercarea edometrica
Fig.3.3.Incercarea edometrica
Determinarea in laborator a compresibilitatii consta in masurarea deformatiei pe
verticala a probelor si a evaluarii in timp a acestora sub efectul incarcarilor verticale
aplicate in trepte.
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• 3.2.1.1.Curba compresiune- tasare ( )
Fig.3.4.Curba compresiune-tasare
%zz
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• 3.2.1.2.Curba de consolidare
Fig.3.5.Curba de consolidare
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• 3.2.1.3.Curba de compresiune-porozitate
Fig.3.6.Curba compresiune-indicele porilor
n
ne
1s
p
V
Ve
t
p
V
Vn
iii e
e
A
A
h
h
V
V
1
1 00
""1 0
LIe
e
h
h
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• 3.2.1.4.4. Curba de compresiunie-tasare specifica
Fig.3.7.Curba compresiune-tasare (sc.liniara)
1 ' ' '
' '
m
ref
oed oed
ref
c ctgE E
c ctg
ref
oedE 1 ' 100ref refp kPa
50
ref ref
oedE E 4ref ref
u oedE E
(m=0.5 pentru nisipuri, m=1 pentru argile moi)
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• -modulul de edeformatie edometric
• M
• - modulul de compresiune volumica ( )
O propunere interesanta pentru calculul lui Es este propunerea lui Ohde(1959)
- modul tangent ; w,v= f(Teren)
Fig.3.8 Evaluarea modului de deformatie (tangent)
2
2
2
132 /3;/2 cmdaNcmdaN zz
Mmv
1 vm
cW
at
zatmes vE )(
'
z
zii tgM
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• Deformatia specifica a probei edometrice
-incercare edometrica (compresiune unidimensionala)
s
zz
Eh
h
0
-legea lui Hooke (LH)
-incercare triaxiala (TE)
)(1
yxzzE
-legea lui Hooke generalizata (LHG)
:yx )2(1
xzzE
)2(1
xz
s
z
EE
2
0
2(1 2 ) 1
1
xs OED OED
z
E E E E M
ITzIEz )()(
Rezulta OEDE E
CONFORM NP112/04 0 1M
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-incercarea edometrica : 0 yx
0)(1
zyxxE
x y ( ) 0;x x z
zx )1(
10K
z
x
“LHG”
0;x y
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65.0
,0,0 OCRKK NCOC (Mayne,2006)
OCRK )'sin1(0 (SR EN 1997/2006)
Fig.3.9 Variatia coef. de impingere in stare de repaos in functie de raportul de supraconsoldare
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,c z tp z
0 ,z a t
NORMAL CONSOLIDAT SUPRACONSOLIDAT
Fig.3.10. Starea pamantului
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• Raport de supraconsolidare
<1 – pamant subconsolidat
=1 – pamant normal consolidat
1.1...2 – pamant usor consolidat
2.1...4 – pamant moderat consolidat
>4 – pamant supraconsolidat
( ) c
z
pRSC OCR
z z
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• 3.5 Comportare tasare – timp in incercarea edometrica
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• 3.6.Factori care influenteaza curba CT
Fig.3.11 Legatura Es de gradul de indesare D (pam.necoezive)
minmax
max
nn
nnD
: n =nmin
: n =nmax
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Umflarea pamanturilor argiloase(PCUM)
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3.8.Incercarea monoaxiala
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Fig.3.21 Curba compresiune –tasare specifica
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Fig.3.23.Calculul modulului de deformatie liniara
- modul tangent:
-modul secant:
00 ctgE
ss ctgE
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INCERCAREA TRIAXIALA
Aparat triaxial
Etape:
1). Tensorul sferic (consolidare)
321 2). Aplicare deviator (rupere)
1
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Tipuri de incercari:
1.Incercare neconsolidata-nedrenata (UU)
-creste );( 31 .3 const
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2.Incercarea consolidata-nedrenata (CU)
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3.Incercarea consolidata-drenata (CD)
-drenare –viteza mica de deformatie compresiune (k)
-v=0.001 mm/min -argile cu plasticitate mare
-v=0.01 mm/min -argile cu plasticitate redusa
-v=0.1 mm/min -nisip
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• Modelul Hardening Soil Model (HSM) in care se determina modulul de
deformatie (folosit in principal la calculul sprijinirilor) refE50
350 50
'cos ' 'sin '( )
'cos ' sin '
m
ref
ref
cE E
c p
Pentru pref=100 kPa
-
'
50 EE modulul MC (PIMC)
urur EE modulul MC (REMNC)
![Page 45: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/45.jpg)
1 3 1 3 cos22 2
1 3 sin 22
2 2
21 3 1 3
2 2
cercul lui Mohr
0
0
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Rezistenta la forfecare este exprimata pe baza teoriei frecarii.
Parametri de baza sunt:
φ’- unghiul frecarii interne
μ- coeficientul de frecare
c’- coeziunea Pamanturi coezive Pamanturi necoezive
4. REZISTENTA LA FORFECARE A PAMANTURILOR
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'f tg => Legea lui Coulomb (1773)
'f tg
4.1 Pamanturi necoezive
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4.1.2.Pamant necoeziv-indesat
mine
Fenomenul de afanare a pamanturilor (nisipoase) indesate prin forfecare, poarta
numele de “DILATANTA”.
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4.1.3.Pamanturi argiloase
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PLP- f proportional cu cA si '
Aria de contact creste cu tensiunile ' si ramane constanta la descarcare
coeziune efectiva (creste odata cu preincarcarea si nu se mai
modifica decat odata cu modificarea umiditatii)
ee Kc (rezistenta la forfecare statica)
e presiunea echivalenta (ef.necesar unei probe NC pentru a avea aceeasi
umiditate cu proba analizata)
K constanta )( pIf
Rezulta : '' ( )f e e ctg c c
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PRINCIPIUL PRESIUNILOR EFFECTIVE
P F uA
/ /P A F A u
' u
In termenii tensiunilor effective:
Deschis la t=0
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4.2.Tipuri de incercari
INCERCAREA DE FORFECARE DIRECTA
Forfecare directa(DST) Forfecare directa simpla(DSS)
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4.2.2.Procesul de forfecare in raport cu natura si starea fizica a pamantului
I.Nisip afanat, argila normal consolidata sau slab consolidata (RSC<2)
IIa.Nisip indesat/argila supraconsolidata (RSC>2) cu structura floculara(fete-muchii)
IIb.Argila supraconsolidata cu structura dispersa
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Tipuri de incercare de forfecare
A. Incercarea UU -Neconsolidata – Nedrenata ,u uc
Incercarea CU -Consolidata –Nedrenata ddc ,
B. Incercarea CD -Consolidata –Drenata ',' c
Nota: Conform notatiilor adoptate de Societatea Internationala de Mecanica
Pamanturilor indicii U,C,D reprezinta prima litera a cuvintelor : undrained,
consolidated, drained.
Pamanturi coezive:
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A.Parametri de forfecare pentru stare nedrenata :
' ' 'f tg c
![Page 56: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/56.jpg)
B.Parametri de forfecare (drenat):
Parametri de forfecare reziduali si de varf '
r rc'si ' 'csi
![Page 57: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/57.jpg)
Factori de influenta – Efectul DILATANTEI / CONTRACTANTEI
Reprezentarea dreptei caracteristice (neliniara)
Porozitate (ecr)
' cr (0.8 )
![Page 58: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/58.jpg)
5432136'
= corectie pentru forma particulei 1
61
21
pentru “sfericitate mare” si forma rotunda a particulei
pentru “sfericitate mica” si forma nerotunda (cu unghiuri) a
particulei
=corectie pentru marimea particulei 2
pentru d>2.0mm (pietris)
pentru 2.0>d>0.6mm (nisip mare)
pentru 0.6>d>0.2mm (nisip )
pentru 0.2>d>0.06mm (nisip fin)
112
92
42
02
=corectie pentru neuniformitate ( coefficient de neuniformitate) 3
pentru Cu>2.0 (neuniformitate mica) 23
13
03
pentru Cu=2.0 (neuniformitate medie)
pentru Cu<2.0 (neuniformitate mare)
Efectul starii :
![Page 59: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/59.jpg)
=corectie pentru gradul de indesare (ID)
pentru 0< ID <0.5 (indesare mica)
pentru 0.5< ID <0.75 (indesare medie)
pentru 0.75< ID <1.00 (indesare mare)
04
14
44
4
=corectie pentru tipul de mineral 5
pentru cuart
pentru feldspat, calcit
pentru muscovite mica
05
45
65
FA ID<15%
A 15 50
M 50 70
I 70 85
FI 85 100
![Page 60: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/60.jpg)
![Page 61: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/61.jpg)
Parametri de forfecare reziduali :
![Page 62: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/62.jpg)
Valorile rezistentei la forfecare folosite in proiectare
a.Studiul stabilitatii versantilor
Tipul de argila si de
miscare
Tipul de
rupere
Deplasari la
rupere
Parametri rezultate
Argila moale scurta mari c
Argila sensitive
-rupere initiala
-curgere a masei
scurta
f.Scurta
mari (5-15%)
f.Mari
0
0
Argila supraconsolidata
-alunecari primare
-intacta
-fisurata cu oglinzi de
frictiune
-alunecari secundare
-curgere lenta
scurta
lunga
scurt
lung
oricare
f.lung
mici
mari
mici
mari
oricare
f.mari
0
0
0
0
0
'
uS
uS
v'vfvS '
vf'
vf'
r'
r'
![Page 63: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/63.jpg)
4.2 INCERCAREA TRIAXIALA
h
h1
0
0 0
;iv
V VV
V V
![Page 64: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/64.jpg)
Aparat triaxial:
![Page 65: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/65.jpg)
NOTA: Se va reprezenta diagrama
h
h
2
31 si
h
h
V
V
pentru diferite valori a efortului de consolidare 3
kPa1003
kPa3003
kPa6003
Se determina :
-Parametri de forfecare
-Caracteristica de dilatare
-Drumul de eforturi in sistemul q-p
-Determinarea modulului de deformatii la cresteri mici a
deformatiei specifice verticale
1 31
2q
1 v
)()( 301 E
![Page 66: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/66.jpg)
Relatia q-ε si ε1 – εv in incercarea triaxiala:
![Page 67: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/67.jpg)
Incercarea de tip CD:
-Etapa 1 – Consolidare :
- Etapa 2 – Rupere
1 3' '
1 '
![Page 68: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/68.jpg)
La incercarea de tip CU (probe normal consolidate) :
![Page 69: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/69.jpg)
Determinarea unghiului de frecare interna si a coeziunii
Daca cunoastem M* si c* putem determina si c’ '
*6
*3arcsin'
M
M
'cos6
'sin3*'
cc
![Page 70: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/70.jpg)
Determinarea modulului de deformatie in modelul Duncan-Chang (modul de rupere)
m
ref
ref
ururc
cEE
'cot'
'cot''
3
m
ref
ref
c
cEE
'cot'
'cot''
35050
m
ref c
cEE
'cot'
'cot''
15050
; INC.TRIAXIALA
; INC. MONOAXIALA KParef 100 5.0m
![Page 71: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/71.jpg)
uu
u
sc
0
cu kc c
'
'
k
kc c
Domenii de folosire a parametrilor de forfecare
Tipul de
incercare
Parametri dreptei intrinseci Corespunde in practica la
situatiile:
UU
Inaltarea rapida a unei c-tii
sau lucrari de pamant pe un
teren neconsolidat,putin
permeabil
CIU
Supraetajarea unei cladiri
sau suprainaltarea unei c-tii
de pam.
Stabilitatea imediata a
taluzurilor sau versantilor.
CAKo-D
Stabilitatea in timp a
taluzurilor si versantilor.
Realizarea in ritm lent a unor
c-tii sau lucrari de pamant pe
terenuri permeabile.
Reamorsarea unor alunecari
dupa suprafete formate
anterior
0',' rr c
![Page 72: Curs Iit Partea 1](https://reader031.fdocument.pub/reader031/viewer/2022012302/5572130d497959fc0b917f93/html5/thumbnails/72.jpg)
', 'k kc
,
' '
' '
', '
cu cu
cu k
cu k
k k
c
c c
c
,
' '
' '
', '
cu cu
cu k
cu k
k k
c
c c
c
cuc
0 1 2 3 4
Lenta
CID
Stabilitatea in timp a
taluzurilor si
versantilor.Realizarea
in timp lent a unor c-tii
sau lucrari de pamant
in terenuri permeabile
CAKo-D
Forfecare simpla (pura)
CAKo-U
CAKo-D
Realizeaza o stare de
eforturi unitare pe tot
cuprinsul probei.
Forfecare in conditii de
deformare plana
CAKo-U Modeleaza mai corect
conditiile din: ramblee
lungi, a pamantului din
diguri, baraje sau din
spatele zidurilor de
sprijin
CAKo-D
Compresiune
monoaxiala
UU Valori orientative
Verificarea stabilitatii versantilor + taluzelor