Soil Liquefaction

Jonathan D. Bray, Ph.D., P.E.

Faculty Chair in Earthquake Engineering Excellence University of California, Berkeley

Primary Sponsor: National Science Foundation

OUTLINE

Liquefaction Concepts

1999 Kocaeli, Turkey EQ

2010-2011 Canterbury, New Zealand EQs

Recommendations

SOIL LIQUEFACTION

LIQUEFACTION

1964 Niigata, Japan EQ (from H.B. Seed) 1906 San Francisco EQ (Lawson et al. 1908)

1989 Loma Prieta EQ

Lower San Fernando Dam- 1971 San Fernando EQ From H.B. Seed

Lower San Fernando Dam- 1971 San Fernando EQ From H.B. Seed

LIQUEFACTION EFFECTS

Flow Liquefaction Cyclic Mobility (strain-softening large strain) (strain-hardening limited strain)

LIQUEFACTION Factor of Safety (FS)

Youd et al. 2001 based on Seed et al. 1985

CRR

Liquefaction Effects Observed at Ground Surface No Liquefaction

Effects Observed at Ground Surface

FS = CRR / CSR CSR

FS =1.2

FS =1.2

LIQUEFACTION EFFECTS

Idriss & Boulanger 2008

Flow Liquefaction

Cyclic Mobility

Post-Liquefaction Residual Strength

Idriss & Boulanger 2008

15

Soil Layering: Human-Made and Geologic

Lower San Fernando Dam: H.B. Seed

Liquefaction-Induced Building Movements March 11, 2011 Tohoku, Japan Earthquake (Mw = 9.0)

Tokimatsu et al. & GEER ( Ashford et al.)

30 cm 70 cm = 30 cm + 40 cm

Measured Displacements in Model Tests

Structure B during Large Port Island event - Test 3-30 Dashti et al. 2010a & 2010b

Large Port Island Event

3 m liquefiable layer

21 m dense sand

2 m dense sand

Building Settlement in Thick Liquefiable Soil Deposits

- Dashti et al. 2010

Bray and Dashti 2010

Dashti et al. 20100

Building Settlement is not Proportional to Thickness of Liquefied Layer

DISPLACEMENT MECHANISMS 1. Volumetric Deformations

Partial Drainage (p-DR) Sedimentation (p-SED) Consolidation (p-CON)

2. Shear-Induced Deformations

Bearing Capacity Failure (q-BC)

SSI-Induced Ratcheting (q-SSI)

3. Ground Loss due to Ejecta

COMMON APPROACH: Estimate Liquefaction-Induced Free-Field Settlement of Level Ground

Ishihara & Yoshimine 1992

= (v)(h)

Dr = 60% FSl = 0.6

Dr = 40% FSl = 0.4

Dr = 90% FSl = 2.5

Nonliquefiable

Estimates 1D settlements due to post-liquefaction volumetric reconsolidation

No shear-induced displacements

Does not estimate building movement

1999 Kocaeli EQ (Mw = 7.5): Adapazari FIELD OBSERVATIONS OF LIQUEFACTION EFFECTS

Buildings Displace Relative to Surrounding Ground

166 CPT/SCPTu & 61 BORINGS with SPT

< http://peer.berkeley.edu/turkey/adapazari >

Fieldwork in Adapazari (Bray et al. 2004)

Accelerometers

Strain Gages

)()( tAEtF == dttAtV )()(

=

=

=ftt

t

dttVtFEFV0

)()(

6060

EFVNN =

Measured Force and Velocity

05

10

15

40 50 60 70 80

Energy Ratio (%)

Ro

d L

en

gth

(m

)

0

5

10

15

40 50 60 70 80

Energy Ratio (%)

Ro

d L

en

gth

(m

)

N-value = 4 N-value = 10

Correction factors

(Skempton, 1986)

Correction factors

(Skempton, 1986)

SPT Short-Rod Correction

Sancio & Bray 2005

Building Response in Adapazari - 1999 Kocaeli EQ

SITE C - Generalized Subsurface Profile D

epth

(m)

Ground Failure No Ground Failure

Photos by Idriss

20

30

40

50

60

70

0 10 20 30 40 50 60 70Percent weight corresponding to 5m

Liqu

id L

imit

SusceptibleModerate SusceptibilityNot Susceptible

Susceptible if wc > 0.9LL

Not Susceptible

Liquefaction Susceptibility of Fine-Grained Soils

Chinese Criteria (Seed & Idriss 1982; Youd et al. 2001):

Liquefaction can only occur if:

1) LL < 35 , 2) wc > 0.9 LL, & 3) Material Finer than 5 m < 15%

CTX Testing by Bray & Sancio 2006

Liquefaction Susceptibility of Fine-Grained Soils

Bray & Sanco (2006)

PI 12 & wc / LL 0.85

Ishihara (1996)

PI 10 - CRRs are similar

0

10

20

30

40

50

0.4 0.6 0.8 1.0 1.2 1.4wc/LL

Pla

stic

ity In

dex

Susceptible to LiquefactionModerate SusceptibilityNot Susceptible

Idriss & Boulanger (2008)

PI < 7

Liquefaction of Fine-Grained Soils

Bray & Sanco (2006)

cyclic response of low plasticity fine-grained soils that are similar to that of sands are also called liquefaction

Idriss & Boulanger (2008)

the term liquefaction should be used only for soils that are evaluated through penetration tests

Bray & Sancio (2008) & Boulanger & Idriss (2008) Perform cyclic tests on slightly plastic soils as undisturbed samples can be retrieved

Test because empirical field methods have limited data

Thin- Walled Piston Sampler

Undisturbed Soil Sampling & Testing

Careful Handling

Cut Extrude Test

-40-30-20-10

010203040

-5 -4 -3 -2 -1 0 1 2 3 4 5Axial Strain, a (%)

Dev

iato

r Stre

ss, q

(kP

a) J5-P3A LL = 27 PI = 7

e = 0.75

cycle 1

cycle 13

-40-30-20-10

010203040

-5 -4 -3 -2 -1 0 1 2 3 4 5Axial Strain, a (%)

Dev

iato

r Stre

ss, q

(kP

a) D5-P2A LL = 25 PI = 0

e = 0.83

cycle 1

cycle 11

-40-30-20-10

010203040

-5 -4 -3 -2 -1 0 1 2 3 4 5Axial Strain, a (%)

Dev

iato

r Stre

ss, q

(kP

a) A6-P10A LL = 44 PI = 18 e = 1.09

cycle 139

cycle 1

-40-30-20-10

010203040

-5 -4 -3 -2 -1 0 1 2 3 4 5Axial Strain, a (%)

Dev

iato

r Stre

ss, q

(kP

a) A6-P6A LL = 38 PI = 11 e = 0.94

cycle 15

cycle 1

Bray & Sancio 2006

Reconstituted

Soil Specimens

CSS Testing:

Soil G has PI = 10

PI = 2 PI = 5

PI = 11

PI = 14 PI = 7

Donahue et al. 2007

Cyclic Resistances of PI = 2 & PI = 10 Soils

Slurry Deposition CSS Testing v 137 kPa Donahue et al. 2007

Evaluation of Ic > 2.6 Criterion

A liquefaction site in Adapazari (Bray & Sancio 2009)

2.6 12 0.85

Canterbury EQs: Widespread Liquefaction

Cubrinovski et al. 2011

Liquefaction Effects in Christchurch

From M. Cubrinovski

4 Sept 2010

(Mark Quigley: Avonside; R. Green)

22 Feb 2011

16 April 2011 13 June 2011: Part

1

13 June 2011: Part 2

Repeated Liquefaction Events

CTUC Building Liquefaction-Induced Differential Settlement Induces Distress

GEER: Bray, Cubrinovski et al.

Building Settlement (cm) Maximum Angular Distortion 1 / 50

490

7 8 11 20 6

31

Ejecta

0

CTUC Building: Christchurch EQ

2011 Christchurch EQ: Robertson & Wride (1998)

N

CTUC Building Settlement

~40 cm ~15 cm

Actual Settlement

~15 cm ~10 cm ~5 cm

Robertson & Wride (1998) & Zhang, Robertson et al. (2002)

SA Building Liquefaction-Induced Differential Settlement Induces Distress

GEER: Bray, Cubrinovski et al.

2011 Christchurch EQ: Robertson & Wride (1998)

SA Building: Christchurch EQ

0 0.5 1 1.5 2

0

1

2

3

4

5

6

7

FS

Dep

th (m

)

0 5 10 15 20

0

1

2

3

4

5

6

7

Settlement (cm)

4 SEP 1026 DEC 1022 FEB 1113 JUN 11

SA Building: Sensitivity of Results

Robertson & Wride (1998) & Zhang, Robertson et al. (2002)

CPT Z8-7

Observed Settlement 10 cm - 25 cm

FSBC 1

PWC Building Liquefaction-Induced Differential Settlement and Tilt

GEER: Bray, Cubrinovski et l

21 stories on basement mat

PWC Building

2011 Christchurch EQ: Robertson & Wride (1998)

Nonlinear Effective Stress Analyses based on Testing

FLAC Analyses with UBC-Sand: Model A in Test T3-50 large P.I. event

0 1 2 3 4 5 6 7 8 9 10-30

-20

-10

0

10

20

30

Time (sec)

She

ar S

train

(%)

Arulmoli CSS TestUBCSAND1 Calibration

She

ar S

trai

n (%

)

Time (sec)

Nevada Sand CSS tests Arulmoli et al. 1992 Dr = 63%, CSR = 0.3, K = 0

Cal

cula

ted

Sett

lem

ent (

mm

)

Maximum Shear Strain

CONCLUSIONS Liquefaction can severely damaged earth structures

and buildings & utilities

Shallow liquefiable soils can lead to much building damage, especially when ejecta occurs

Cyclic mobility occurs for PI 12 & wc/LL 0.85 soil

Building settlement is not proportional to the thickness of the liquefiable layer

Shear-induced deformation is critical mechanism

Simplified procedures do not capture the observed performance of heavy structures with shallow foundations

RECOMMENDATIONS

Perform cyclic testing on fine-grained soils that can be sampled effectively to assess their seismic response characteristics.

0

10

20

30

40

50

0.4 0.6 0.8 1.0 1.2 1.4wc/LL

Pla

stic

ity In

dex

Susceptible to LiquefactionModerate SusceptibilityNot Susceptible

Liquefaction triggering procedures, which have been developed for sands and nonplastic silty sands, should be applied with judgment.

Bray & Sancio 2006

RECOMMENDATIONS For level ground conditions with no free-face:

Pile foundation with its neutral plane in firm ground below the liquefiable layer will not settle significantly

Shallow foundation with deep liquefiable layer will largely undergo volumetric reconsolidation that can be estimated using 1D procedures

Shallow foundation with shallow liquefiable layer can undergo largely shear-induced movements that cannot be estimated using available 1D procedures

Effective stress analyses based on good earthquake & soil characterization can provide useful insights

RECOMMENDATIONS For earth structures and sloping or free-face ground:

Key issue is are there materials that will lose significant strength as a result of earthquake shaking

Evaluate post-liquefaction residual strength of liquefied soils and calculate FS to investigate flow slide potential

Employ effective mitigation measures, if required

Effective stress analyses based on good earthquake & soil characterization can provide useful insights

Assess earth structure and in situ ground as a system (e.g., void redistribution and thin water films)

Boulanger, R.W., and Idriss, I.M., Closure to Liquefaction Susceptibility Criteria for Silts and Clays, J. of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 134, No. 7, July, 2008, pp. 1027-1028.

Bray, J.D. and Sancio, R.B., Assessment of the Liquefaction Susceptibility of Fine-Grained Soils, J. of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 132, No. 9, Sept., 2006, pp. 1165-1177.

Bray, J.D. and Sancio, R.B., Closure to Assessment of the Liquefaction Susceptibility of Fine-Grained Soils, J. of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 134, No. 7, July, 2008, pp. 1031-1034.

Bray, J.D. and Sancio, R.B., Performance of Buildings in Adapazari during the 1999 Kocaeli, Turkey Earthquake, in Earthquake Geotechnical Case Histories for Performance Based Design, Kokusho, T, Ed., TC4 Committee, ISSMFE, CRC Press/Balkema,The Netherlands, pp. 325-340 & Data on CD-ROM, 2009.

Donahue, J.L., Bray, J.D., and Reimer, M.F. Liquefaction Testing of Fine-Grained Soil Prepared Using Slurry Deposition, Proc. 4th Inter. Conf. Earthquake Geotechnical Engineering, Paper No. 1226, June 25-28, 2007.

Idriss, I.M, and Boulanger, R.S. Soil Liquefaction During Earthquakes. Earthquake Engineering Research Institute, EERIMNO-12, Oakland, CA, 2008.

Sancio, R.B. and Bray, J.D., An Assessment of the Effect of Rod Length on SPT Energy Calculations Based on Measured Field Data, Geotechnical Testing Journal, ASTM, Vol. 28(1), Paper GTJ11959, pp. 1-9, Jan. 2005.

Seed, R.B., Cetin, K.O., Moss, R.E.S., Kammerer, A.M., Wu, J., Pestana, J.M., Riemer, M.F., Sancio, R.B., Bray, J.D., Kayen, R.E., and Faris, A. Recent Advances in Soil Liquefaction Engineering: A Unified and Consistent Framework, 26th Annual ASCE Los Angeles Geotechnical Spring Seminar, Keynote Presentation, Long Beach, Calif., April 30, 2003.

References

Soil LiquefactionOUTLINELIQUEFACTIONLower San Fernando Dam- 1971 San Fernando EQLower San Fernando Dam- 1971 San Fernando EQSlide Number 6LIQUEFACTION Factor of Safety (FS)Post-Liquefaction Residual StrengthSlide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Evaluation of Ic > 2.6 Criterion Canterbury EQs: Widespread LiquefactionLiquefaction Effects in Christchurch Repeated Liquefaction EventsCTUC BuildingLiquefaction-Induced Differential Settlement Induces DistressCTUC Building: Christchurch EQCTUC Building SettlementSA BuildingLiquefaction-Induced Differential Settlement Induces DistressSlide Number 39SA Building: Sensitivity of ResultsPWC BuildingLiquefaction-Induced Differential Settlement and TiltPWC BuildingSlide Number 43Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48