Practitioner’s Overview:
Piles in Liquefied Soil
Timothy C. Siegel, P.E., G.E., D.GE
Dan Brown and Associates PC
DAN
BROWN
ASSOCIATESAND
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)
http://en.wikipedia.org/wiki/File:Liquefaction_at_Niigata.JPG
http://en.wikipedia.org/wiki/File:Liquefaction_at_Niigata.JPG
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.
//upload.wikimedia.org/wikipedia/commons/5/57/Showa_bridge_Niigata_NGDC.JPG
//upload.wikimedia.org/wikipedia/commons/5/57/Showa_bridge_Niigata_NGDC.JPG
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 c
