E R Ground Deformation and Lateral Spreading · 2012. 8. 22. · Evaluation of flow slide potential Static, limit equilibrium analysis Requires residual strength ~100 psf ~400 psf

PPEEEERR Ground Deformation and

Lateral Spreading

Steve KramerUniversity of Washington

2001 Annual Meeting

2001 Annual Meeting

Geotechnical Impacts on Structural PerformanceGeotechnical Impacts on Structural Performance

Response modification

Soil conditions can change:� Amplitude� Frequency content� Duration

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Ground failure

Permanent deformations

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Ground failure

Permanent deformationsFlow failure

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Ground failure

Permanent deformationsFlow failureLateral spreading

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Ground failure

Permanent deformationsFlow failureLateral spreadingSettlement

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Evaluation of Liquefaction HazardsEvaluation of Liquefaction Hazards

Three primary questions to consider:

Is the soil susceptible to liquefaction?

Will the anticipated loading trigger liquefaction?

What will be the effects of liquefaction?

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Liquefaction SusceptibilityLiquefaction Susceptibility

Geologic environments well established

Fluvial deposits Alluvial deposits

Man-made deposits

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Liquefaction SusceptibilityLiquefaction Susceptibility

Soil types well established:� Clean sands� Silty sands (up to ~35% fines)

Also observed:� Silts� Gravelly soils

Conclusion:

Liquefaction susceptibility isrelatively well understood �not a pressing issue fordevelopment of PBEE

2001 Annual Meeting

Initiation of LiquefactionInitiation of Liquefaction

Current procedure:

Characterize loading by cyclic shear stress

rg

aCSR d'v

vmax

ó

ó0.65=

ó0.65

'v

maxτ=CSR

and earthquake magnitude

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Current procedure:

Characterize resistance by cyclic shear stress

CRR

(N1)60, qc1, Vs1, �

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Current procedure:

Characterize resistance by cyclic shear stress

CRR

(N1)60, qc1, Vs1, �

Liquefaction

No Liquefaction

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Advantages of current procedure:� Experience shows it works� It is widely embraced by practitioners

Limitations of current procedure:� No insight into uncertainty� Mixes source (M) and site (amax) parameters� Pore pressures related to strains more than stresses

Conclusion:

Practical procedures for evaluation of liquefactionpotential exist, but are not readily suited toimplementation in PBEE framework, in whichunbiased estimates of probability of liquefactionare required.

More high-quality field data from sites ofliquefaction and non-liquefaction are needed.

Improvements are possible through theidentification of better parameters with which tocharacterize loading and resistance.

2001 Annual Meeting

What are we doing about these issues?What are we doing about these issues?

Liao et al (1988)

0.0

0.5

CRR

0 40(N1)60

Youd et al (1998)

0.0

0.5

CRR

0 40(N1)60

Toprak et al (1999)

0.0

0.5

CRR

0 40(N1)60

Seed et al (2001)

0.0

0.5

CRR

0 40(N1)60

Probabilisticevaluation ofliquefaction potentialSeed, DerKiureghian, et al.

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Ground Failure andBuildingPerformance inAdapazari, TurkeyBray et al.

http://www.eerc.berkeley.edu/turkey/adapazari/data/site_a/index.html

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Effects of LiquefactionEffects of Liquefaction

Effects can be divided into two categories:

Response� Amplitude� Frequency content� Duration

Ground Failure� Lateral deformations� Vertical deformations

Both are influencedby phase

transformationbehavior of soil

Dilative

Dilative

Contractive

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Phase transformation

� Contractive behavior � u increases, p� decreases

� Dilative behavior � u decreases, p� increases

q

p�

Phase transformation line

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Stress-strain Stress path

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∆uHigh

stiffness

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∆uHigh

stiffness

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After several more cycles �

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∆u

Lowstiffness

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Higherstiffness

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Stiffness changesdramatically over

the course of acycle of loading

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Stiffness changesdramatically over

the course of acycle of loading

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ResponseStiffness generally decreases

� Longer period motion� Lower acceleration amplitudes� Higher displacement amplitudes

Highfrequency

Lowfrequency

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Phase transformationIncreasing stiffness with strain�De-liquefaction shock waves�

Wildlife Array

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Ground failure - permanent deformations

HorizontalLateral spreadingFlow slides

VerticalSettlement

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Lateral spreading

Estimation of permanent displacement

log DH = -17.614 + 1.581 M � 1.518 log R*- 0.011 R + 0.343 log S + 0.547log T15

+ 3.976 log (100 � F15)� 0.923 log (D5015 + 0.1mm)

Based solely on regression

Provides only ground surface displacement

N

DH

15

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Lateral spreading

Loose layer

Initialshearstress

Lateral spreading

What controls displacements?What controls displacements?

Phase transformation behaviorPhase transformation behavior

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-4

-3

-2

-1

0

1

2

3

4

5

-10 -5 0 5 10 15

Shear Strain (%)

Shear Stress (kPa)

-4

-3

-2

-1

0

1

2

3

4

5

0 10 20 30 40 50

Effective Vertical Stress (kPa)

She

ar S

tres

s (k

Pa)

Conclusions:

We must be able to model phase transformation behavior to predict theperformance of structures located on ornear sites where lateral spreading canoccur.

We need more experimental data on phase transformation behavior and the factors that affect it.

We need more high-quality field data on lateral spreading case histories

Conclusions:

We must be able to model phase transformation behavior to predict theperformance of structures located on ornear sites where lateral spreading canoccur.

We need more experimental data on phase transformation behavior and the factors that affect it.

We need more high-quality field data on lateral spreading case histories

2001 Annual Meeting

Evaluation of Post-LiquefactionResidual Strengthand Stress-StrainBehaviorSeed, Pestana,Kammerer

http://www.ce.berkeley.edu/~kammerer/nevada.html


2001 Annual Meeting

Modeling of LateralSpreading and Effects onFoundations and Super-structureElgamal, Yang


Middle Channel bridgeat Humboldt Bay

2001 Annual Meeting


Liquefaction-Induced GroundDeformation andFailureBardet

http://geoinfo.usc.edu/gees/

2001 Annual Meeting


Lateral spreading can cause damage to pile foundations

Conclusions:

We need to be able to predict the distribution of lateral spreading deformations with depth.

Conclusions:

We need to be able to predict the distribution of lateral spreading deformations with depth.

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Centrifuge Modeling ofCyclic Mobility andLateral SpreadingKutter, Dafalias


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Seismic Performance ofPile-Supported WharfStructuresDickenson, Kutter,McCullough,Schlechter


Centrifuge Model

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Flow slidesOccur relatively rarelyInvolve very large deformationsTremendously damaging

Fort Peck Dam>1200 ft displ

San Fernando Dam>200 ft

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Flow slidesEvaluation of flow slide potential

Static, limit equilibrium analysisRequires residual strength

~100 psf

~400 psf

Conclusion:

Residual strength, and thefactors that affect it, needsto be better understood.

Uncertainty in residual strength estimation needs to be quantified.

Conclusion:

Residual strength, and thefactors that affect it, needsto be better understood.

Uncertainty in residual strength estimation needs to be quantified.

2001 Annual Meeting


Uncertainty inresidual strengthevaluationKramer

Ring Simple ShearDevice (RSSD)

Innerrings

Outerrings

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Uncertainty inresidual strengthevaluationKramer

0

100

200

300

400

500

600

700

800

900

1000

0 20 40 60 80 100 120 140 160 180

Shear Strain (%)

Sh

ear

Str

ess

(psf

)

Test 1

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200 1400 1600

Normal Stress (psf)

Sh

ear

Str

ess

(psf

)

Test 1

γ = 100%

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The Next Question:The Next Question:

What do we do about liquefaction?� Abandon the site� Improve the site

Conclusion:

Performance-based design procedures for soil improvement are needed

Conclusion:

Performance-based design procedures for soil improvement are needed

2001 Annual Meeting

Performance ofImproved GroundSitar, Hausler

http://www.ce.berkeley.edu/~hausler/home.html


2001 Annual Meeting

SummarySummary

Consideration of liquefaction-related phenomena inPBEE will require:

� Additional laboratory testing of liquefiable soils �focusing on behavior after initial liquefaction

� Model testing of soil-structure systems

� Acquisition of high-quality field performance data

� Development of improved numerical modelingcapabilities

Documents

E R Ground Deformation and Lateral Spreading · 2012. 8. 22. · Evaluation of flow slide potential Static, limit equilibrium analysis Requires residual strength ~100 psf ~400 psf