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Practitioner’s Overview: Piles in Liquefied · PDF file Practitioner’s Overview: Piles in Liquefied Soil Timothy C. Siegel, P.E., G.E., D.GE Dan Brown and Associates PC DAN BROWN

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  • 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