Practitioner’s Overview:

Piles in Liquefied Soil Timothy C. Siegel, P.E., G.E., D.GE

Dan Brown and Associates PC

DANBROWNASSOCIATESAND

2016 Annual Kansas City Special Conference

Ritz Charles Special Events & Conference Facility

Overland Park, KS

April 21, 2016

The

• Liquefaction triggering

• Lateral spread

• Liquefaction-induced compression

• Drag load and downdrag settlement

• Residual strength

• Interaction with inertial loads

1964 Niigata Japan Earthquake (Mw=7.6)

2010 Christchurch, New Zealand Earthquake (Mw=6.3)

Liquefaction Triggering

WATER TABLE FOR LQ ANALYSIS

9%Ground surface

Elevated w.t. (assumed) 48%

Observed w.t. 43%

Survey

Response

Published research (Okamura and Soga, 2006; Hossain et al., 2013) supports that

partially saturated soils have a significantly greater resistance to liquefaction than

saturated soils.

Liquefaction Triggering

Wildlife ground motion

Onset of liquefaction

• Contractive behavior/decrease in void ratio

• Dramatic increase in pore water pressure

• Loss of shear strength

• Change in stiffness (affecting propagation of shear waves)

Liquefaction Triggering

• Idriss, I.M. and Boulanger, R.W. 2008, Soil liquefaction during earthquakes, EERI MNO-12, 235 p.

• Cetin, K.O., Seed, R.B., Der Kiureghian, A., Tokimatsu, K., Harder, L.F., Kayen, R.E. and Moss, R.E.S. 2004, “Standard

penetration test-based probabilistic and deterministic assessment of seismic soil liquefaction potential” ASCE, Journal of

Geotechnical and Geoenvironmental Engineering, 130(12), 1314-1340.

Semi-empirical methods:

• SPT

• CPT

• Shear wave velocity

Semi-empirical methods

Positives:

• Simple

• Widely accepted

Liquefaction Triggering

Semi-empirical methods

Positives:

• Simple

• Widely accepted

Limitations:

• May not reflect soil behavior (SPT)

• Consideration of plasticity (Boulanger and Idriss, 2006; Bray and Sancio, 2006)

• Aging effects (Leon, Gassman, and Talwani, 2008)

• Application to ground improvement verification

Liquefaction Triggering

Liquefaction Triggering

Liquefaction Triggering

(Dilative) If the volumetric strain is

positive at the peak strength then no

liquefaction.

(Contractive) Conversely, liquefaction

will occur if the volumetric strain is

negative at the peak strength.

Lateral Spread

1964 Niigata Japan Earthquake (Mw=7.6)

“The term ‘lateral spreading’ …refers to global movements of soil due to

liquefaction of underlying cohesionless soil..” Recommended Design Practice

for Pile Foundations in Laterally Spreading Ground.

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

• Are the site conditions consistent with the lateral

spread procedure?

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

• Are the site conditions consistent with the lateral

spread procedure?

• How is the kinematic force determined?

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

• Are the site conditions consistent with the lateral

spread procedure?

• How is the kinematic force determined?

• How accurate is the estimate of lateral spread?

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

• Are the site conditions consistent with the lateral

spread procedure?

• How is the kinematic force determined?

• How accurate is the estimate of lateral spread?

• How should the inertial force from the structure be

combined with soil kinematic force?

Lateral Spread

• Will there be lateral spread?

• Limit equilibrium

• Youd et al. (2002)

• Zhang et al. (2004)

• Are the site conditions consistent with the lateral

spread procedure?

• How is the kinematic force determined?

• How accurate is the estimate of lateral spread?

• How should the inertial force from the structure be

combined with soil kinematic force?

• What is conservative enough?

Lateral Spread

LQ soil

w/o LQ w/ LQ

change in response

Lateral Spread

Ashford, S.A., Boulanger, R.W., and Brandenberg, S.J. 2011, “Recommended Design Practice for Pile Foundations in

Lateral Spreading Ground” PEER Report 2011/04, Pacific Earthquake Engineering Research Center, College of

Engineering, University of California, Berkeley, 68 p.

LQ soil

w/o LQ w/ LQ

change in response

50% of inertial load is combined with

lateral spread (Ashford et al., 2011).

Lateral Spread

Ashford, S.A., Boulanger, R.W., and Brandenberg, S.J. 2011, “Recommended Design Practice for Pile Foundations in

Lateral Spreading Ground” PEER Report 2011/04, Pacific Earthquake Engineering Research Center, College of

Engineering, University of California, Berkeley, 68 p.

LQ soil

It is incorrect to displace the pile head to match the

lateral spread and then add the inertial load. Bending

should be de-coupled

Lateral Spread

Ashford, S.A., Boulanger, R.W., and Brandenberg, S.J. 2011, “Recommended Design Practice for Pile Foundations in

Lateral Spreading Ground” PEER Report 2011/04, Pacific Earthquake Engineering Research Center, College of

Engineering, University of California, Berkeley, 68 p.

LQ soil

It is incorrect to displace the pile head to match the

lateral spread and then add the inertial load.

Lateral Spread

LQ soil

Bending should be de-coupled. The resultant moment

distribution should be the combination of the two components..

+

Liquefaction Induced Compression

Ishihara, K. and Yoshimine, M. , “Evaluation of settlements in sand deposits following liquefaction during earthquakes”

(1992) Soils and Foundations, 32, 173-188.

d = S(ev)(Dh)

Assumes:

• Free field

• Level ground

Liquefaction Induced Compression

Ishihara, K. and Yoshimine, M. , “Evaluation of settlements in sand deposits following liquefaction during earthquakes”

(1992) Soils and Foundations, 32, 173-188.

d = S(ev)(Dh)

Assumes:

• Free field

• Level ground

It may be incorrect to

conclude that the

estimated settlement

are reasonable

estimates of the

actual settlement.

Probably more

reasonable to use

settlement as a

relative measure of

the degree of risk.

Liquefaction Induced Compression

2010 Christchurch, New Zealand Earthquake (Mw=6.3)

Picture courtesy of Dr. Jonathan D. Bray, University of California, Berkeley

with Dr. Misko Cubrinovski, PhD, University of Canterbury

Drag Load and Downdrag Settlement

http://www.geerassociation.org/GEER_Post%20EQ%20Reports/Kobe_1995/

Drag Load and Downdrag Settlement

Pile Pile Pile

Neutral

plane

Static Conditions

LQ soil

Drag

Load

• Decrease in geotechnical FOS

• Decrease in drag load

• No pile settlement

Shallow LQ Deep LQ

LQ soil

• Decrease in geotechnical FOS

• Pile settlement ~ LQ compression

Fellenius, B.H. and Siegel, T.C. 2008, “Pile design consideration in a liquefaction event” ASCE, Journal of Geotechnical

and Geoenvironmental Engineering, 132(9), 1412-1416.

reduce

shear

reduce

shear

Drag Load and Downdrag Settlement

Pile Pile Pile

Neutral

plane

Static Conditions

LQ soil

Drag

Load

• Decrease in geotechnical FOS

• Decrease in drag load

• No pile settlement

Shallow LQ Deep LQ

LQ soil

• Decrease in geotechnical FOS

• Pile settlement ~ LQ compression

Fellenius, B.H. and Siegel, T.C. 2008, “Pile design consideration in a liquefaction event” ASCE, Journal of Geotechnical

and Geoenvironmental Engineering, 132(9), 1412-1416.

reduce

shear

reduce

shear

Drag Load and Downdrag Settlement

Pile Pile Pile

Neutral

plane

Static Conditions

LQ soil

Drag

Load

• Decrease in geotechnical FOS

• Decrease in drag load

• No pile settlement

Shallow LQ Deep LQ

LQ soil

• Decrease in geotechnical FOS

• Pile settlement ~ LQ compression

• Plunging only occurs if FOS < 1

Fellenius, B.H. and Siegel, T.C. 2008, “Pile design consideration in a liquefaction event” ASCE, Journal of Geotechnical

and Geoenvironmental Engineering, 132(9), 1412-1416.

reduce

shear

reduce

shear

Residual Strength

Kramer, S.L. 2008, “Evaluation of liquefaction hazards in Washington state” Final Research Report, Agreement T2605,

Task 66 Liquefaction Phase III, 329 p.

The liquefied strength is not zero and

increases with confining stress.

Interaction with Inertial Loads

Kramer, S.L., Sideraas, S.S., and Greenfield, M.W., “The timing of liquefaction and its utility in liquefaction hazard

evaluation” Proceedings, 6th International Conference on Earthquake Geotechnical Engineering, Christchurch.

Onset of liquefaction

Interaction with Inertial Loads

1. “Intensity” that

triggers liquefaction.

Kramer, S.L., Sideraas, S.S., and Greenfield, M.W., “The timing of liquefaction and its utility in liquefaction hazard

evaluation” Proceedings, 6th International Conference on Earthquake Geotechnical Engineering, Christchurch.

Effect on pile, slope,

etc.as a result of the

“Intensity”..

3, Continued “intensity” once liquefaction

occurs. [This intensity will be less than if

liquefaction did not occur.]

2. Non-liquefied “intensity”

during earthquake

Interaction with Inertial Loads

1. “Intensity” that

triggers liquefaction.

Kramer, S.L., Sideraas, S.S., and Greenfield, M.W., “The timing of liquefaction and its utility in liquefaction hazard

evaluation” Proceedings, 6th International Conference on Earthquake Geotechnical Engineering, Christchurch.

Effect on pile, slope,

etc.as a result of the

“Intensity”..

3, Continued “intensity” once liquefaction

occurs. [This intensity will be less than if

liquefaction did not occur.]

2. Non-liquefied “intensity”

during earthquake

This is typically what

we do now.

Interaction with Inertial Loads

1. “Intensity” that

triggers liquefaction.

Kramer, S.L., Sideraas, S.S., and Greenfield, M.W., “The timing of liquefaction and its utility in liquefaction hazard

evaluation” Proceedings, 6th International Conference on Earthquake Geotechnical Engineering, Christchurch.

Effect on pile, slope,

etc.as a result of the

“Intensity”..

3, Continued “intensity” once liquefaction occurs.

[This intensity will be less than if liquefaction did not

occur.]

2. Non-liquefied “intensity”

during earthquake

Interaction with Inertial Loads

1. “Intensity” that

triggers liquefaction.

Kramer, S.L., Sideraas, S.S., and Greenfield, M.W., “The timing of liquefaction and its utility in liquefaction hazard

evaluation” Proceedings, 6th International Conference on Earthquake Geotechnical Engineering, Christchurch.

Effect on pile, slope,

etc.as a result of the

“Intensity” accounting for

liquefaction.

3, Continued “intensity” once liquefaction

occurs. [This intensity will be less than if

liquefaction did not occur.]

2. Non-liquefied “intensity”

during earthquake

• There are several liquefaction considerations in pile design;

Concluding Remarks

• There are several liquefaction considerations in pile design;

• These considerations involve judgment;

Concluding Remarks

• There are several liquefaction considerations in pile design;

• These considerations involve judgment;

• There appears to be upcoming advancements that will better balance safety and

cost – rather than the tendency to always apply the most conservative of design

decisions

Concluding Remarks

• There are several liquefaction considerations in pile design;

• These considerations involve judgment;

• There appears to be upcoming advancements that will better balance safety and

cost – rather than the tendency to always apply the most conservative of design

decisions

• Application of critical state principles to liquefaction triggering.

Concluding Remarks

• There are several liquefaction considerations in pile design;

• These considerations involve judgment;

• There appears to be upcoming advancements that will better balance safety and

cost – rather than the tendency to always apply the most conservative of design

decisions

• Application of critical state principles to liquefaction triggering.

• Consideration of time in designing for liquefaction – inertial load,

deflection,….

Concluding Remarks

THANK YOU FOR

YOUR ATTENTION

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