Topic 4: Topic 4: Shear Strength of Clays: CVEN 7718 CVEN 7718 Engineering Properties of Soils Spring 2010
Topic 4: Topic 4: Shear Strength of Clays: CVEN 7718 CVEN 7718 Engineering Properties of Soils Spring 2010
Topic 4: Topic 4: Shear Strength of Clays: CVEN 7718 CVEN 7718 Engineering Properties of Soils Spring 2010
Topic
4:
Topic4:
ShearStrengthofClays
CVEN7718
CVEN 7718
EngineeringPropertiesofSoils
Spring2010
3c
or
Mean
effective
stress
Volumetric
strain
or
Void ratio
Normally consolidated (NC):
Over-consolidated (OC):
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StressStrainCurvesfromCDTestsonNCClay
StressStrainCurvesfromCDTestsonOCClay
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ResultsfromCDtestsonNCandOCclays
ResultsfromCDtestsonNCandOCclays
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StressStrainCurvesfromCUTestsonNCClay
StressStrainCurvesfromCUTestsonNCClay
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StressStrainandPWPCurvesfromCUTestsonNCClay
StresspathsfromCUTestsonNCclay
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StressStrainCurvesfromCUTestsonOCClay
StressStrainCurvesfromCUTestsonOCClay
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StressStrainCurvesfromCUTestsonOCClay
StresspathsfromCUTestsonOCclay
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StrainsatfailureinCUandCDtests:Simons(1960)
Porewaterpressurecoefficientatfailure
On average, for:
NC Clays, A = _____
OC Clays use charts
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StresspathsfromCUTestsonNCandOC
claysatsame3c
StresspathsfromCUTestsonNCandOCclays
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Effectivestresspaths
Normally consolidated
Over-consolidated
EffectivestressfailureenvelopesforCUtestsonNC
claysandOCclayswiththesame3max
10
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Effectivestressfailureenvelopes:GooseLakeClay
(1 3)f
(1/3)f
NC
OC
Effectivestressenvelopes:SodiumIllite
Failure based on (1 3)
Failure based on (1 / 3)
11
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TotalstressenvelopesforCUtests:Howare
theseconstructed?
TotalstressenvelopesforCUtestsonNCclaysand
OCclayswiththesame3max
12
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Totalstress(R)envelopes
Watercontentstrengthrelationships
13
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StressPathande3Relationships
Rutledge(1947)reporttoUSACOE
Testtypes:
Goal:
14
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Rutledge(1947)reporttoUSACOE
Rutledge(1947)reporttoUSACOE
15
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Rutledge(1947)reporttoUSACOE
EffectofPlasticityIndexonNCClay
16
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EffectofPlasticityIndexonNCClay
Sensitivity:Definitionandorigins
17
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Sensitivity:EffectsonEngineeringProperties
Sensitivity:Identification
18
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SPTandMPSDFailureEnvelopes:LowS
SPTandMPSDFailureEnvelopes:HighS(LedaClay)
19
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Sensitiveclaylandslides
Porewaterpressurecoefficientatfailure(NCclays)
Mean
St. Dev.
Mean
St. Dev.
20
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Thixotropyasasourceforsensitivity
Definition:
Whydowecare?
Mitchell(1976),fromDay(soilscientist)
21
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Thixotropicstrengthregain
LossofcementationasanexplanationforS
22
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SummaryoftheCausesofSensitivity
Peakvs.ResidualStrength
23
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Directsheartestwithreversal
Skempton Directsheartestwithreversal
24
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Ringsheartestsetups
Ringsheartestresults
25
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ResidualfrictionanglesandMineralogy
Residualfrictionangles:allvariables
26
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Mechanismsofresidualshearstrength
Strainrateeffects
Importance
Typesoftests
27
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Creep fractionalloadtests
CreeptestsTimetofailure
28
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Strainrateeffects
Timetofailure(CasagrandeandWilson1951)
Clay
Mexicocity
Bearpaw
Oahe
Cucaracha
29
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Porewaterpressuremigration
NC Clay
OC Clay
Conclusion:
Highspeedloadingsituations:
Impactloading
Cyclicloading
Earthquakes:
Ocean waves:
30
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Fastloading(CasagrandeandShannon1951)
Clay
C b id clay(UU)
Cambridge
l (UU)
Cambridgeclay(6 psiconfining
pressure)
Sand
Fastloading(NC) OlsonandParola(1967)
31
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Fastloading(OC) OlsonandParola(1967)
Earthquakeloading SeedandChan(1966)
32
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EffectsonModulus
OlsonandParola(1967) NCModulus
33
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OlsonandParola(1967) OCModulus
Strainratesofloading
34
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Planestrainevaluations
DuncanandSeed(1966):
Soiltype:
PSC
TXC
HenkelandWade(1966):
Soiltype:
PSC
TXC
Conclusions:
Bishop,WebbandLewin(1965)
Subway
level
C
E
F
35
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Duncan,Horz,andWang(1989)
o
(degrees)
(degrees)
N.A
N.A.
USCS
Relative compaction
w.r.t.standard
Proctor(%)
GW
GP
SW
SP
105
100
95
90
SM
100
95
90
85
SMSC
CL
LeeandMorrison(1970)
36
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Fullysoftenedshearstrength relevance
CollinsandZnidarcic(2004)
37
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Fullysoftenedshearstrength Definitions
Skempton(1970)
Stark,Choi,andMcCone(2005)
,
,
(
)
Stark,Choi,andMcCone(2005)
38
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Inherentanisotropy
(a)
(b)
Inherentanisotropy Drainedstrength
Drained(CD)testsonS.F.BayMud(DuncanandSeed
1966)
39
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Inherentanisotropy Undrained
strengths
Inherentanisotropy Undrainedstrengths
40
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Ward,Marsland,andSamuels(1965):
UUtestsonLondonClay
(1 3)f
(psi)
Depth
(ft)
(1 3)f/(1 3)f0
0
0
45
45
90
90
0
0
45
45
90
90
30
36.6
32.7
51.3
0.89
1.40
50
32.9
19.6
40.4
0.60
1.23
66
44.1
33.2
70.8
0.75
1.61
91
54.4
48.6
84.1
0.89
1.55
114
59.9
50.4
97.8
0.84
1.63
138
81
52.8
107.4
0.65
1.33
Ward,Marsland,andSamuels(1965):
UUtestsonLondonClay
Strengthratio:
Axialstrainatfailure
Vertical:
45degrees:
Horizontal:
41
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Connecticutvalleyvarvedclay
SkemptonandHutchinson(1969)
42
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StressInducedAnisotropy
Anisotropic(K0)Consolidation
43
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c/pRatiosforK0Consolidated,NormallyConsolidatedClay
DuncanandSeed(1966):S.F.BayMud
TXC
TXE
Ratio
Jamiolkowski,Ladd,Germaine,andLancellotta(1985):CH
MarineClay
TXC
TXE
Ratio
Jamiolkowski,Ladd,Germaine,andLancellotta(1985):OC
Jamiolkowski Ladd Germaine and Lancellotta (1985): OC
MarineClay
TXC
TXE
Ratio
DirectSimpleShear:IntermediaryTest
44
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LaddandFoott(1974):BostonBlueClay
Test type
f/v
Planestrainactive
Triaxialcompression
Directsimpleshear
Planestrainpassive
Triaxialextension
Budiman,Sture+Ko(1988):DirectionalShearApparatus
45
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FieldEvaluationofAnisotropy:VaneShear
FieldEvaluationofAnisotropy:VaneShear
Total moment (torque): M = Mv + Mh
46
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FieldEvaluationofAnisotropy:VaneShear
Aasvanesheartests
Site
OCR
Aserum
>1
Drammen
Manglerud
Lierstranda
fh/fv
47
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StressInducedAnisotropy:Factors
(a)
(b)
(c)
DerivationofTheoreticalRelationshipbetween
c/p,A,K0,and:TXE
48
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DerivationofTheoreticalRelationshipbetween
c/p,A,K0,and:PWPgeneration
DerivationofTheoreticalRelationship
betweenc/p,A,K0,and:MohrCoulomb
49
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DerivationofTheoreticalRelationship
betweenc/p,A,K0,and:Synthesis
DerivationofTheoreticalRelationshipbetween
c/p,A,K0,and:Equations
Triaxialextension:
Triaxialcompression:
ForBostonBlueClay:
y
Loading
condition
From
Equations
MeasuredL+F
(1974)
TXC
TXE
50
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DuncanandSeed(1966):Equationsforc/pforany
FailurePlaneOrientation
BjerrumandKenney(1967)
51
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ConclusionsAboutAnisotropy
ConventionalPracticewithUUTests
52
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UUstrengthfromthelabmaybehigher
thanfieldstrength:
UUstrengthfromthelabmaybelowerthan
fieldstrength
53
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SamplingEffects
Changeinstressesduringsampling
54
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Perfectsampling
Perfectsampling
55
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Perfectsampling
SamplingEffects
56
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RecompressionTechnique(NCClay)
RecompressionTechnique(OCClay)
57
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CriteriaforPerfectsampling
SHANSEP(LaddandFoott1974)
58
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NormalizedSoilParameters
SHANSEP(NCClay)
59
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StepsforSHANSEPProcedure(NCClay)
SHANSEP(OCClay)
60
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StepsforSHANSEPProcedure(OCClay)
c/pforOCClays
61
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c/pforOCClays
MesrisApproach
62