Literature on Lquefaction

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    13th World Conference on Earthquake EngineeringVancouver, B.C., Canada

    August 1- 6, 2004Paper No. 2973

    LIQUEFACTION RISK ASSESSMENT AND DESIGN OF PILE

    FOUNDATIONS FOR HIGHWAY BRIDGE

    Nikolaos KLIMIS 1, Anastasios ANASTASIADIS1, George GAZETAS2and Marios APOSTOLOU2

    SUMMARY

    A major 1 km long bridge over Nestos river, currently under construction, is founded on fluvial deposits

    containing potentially liquefiable clean sand and silty sand in a medium-dense to loose state, for a total

    thickness of about 12 m. Geotechnical reconnaissance involved a considerable number of geotechnical

    boreholes, CPT, SPT, Crosshole, and laboratory tests. The total thickness of soil deposits is about 50 m

    and is underlain by good quality gneiss. Three different design profiles are assigned but only one of

    them is used in this paper for 1D equivalentlinear and nonlinear seismic response analyses. Nine actual

    accelerograms, significantly varying in frequency content define the base-rock input motion. Then, current

    state of practice of semi-empirical methodologies based on SPT, CPT and VS profiles, are applied to

    access the safety factor against liquefaction, and are compared with results of theoretical 1D nonlinear

    effective stress analyses. The consequences of liquefaction on foundation piles are determined by

    adopting a methodology inspired by the recent Japanese experience, which calls for three distinct andsuccessive stages: before, during, and after liquefaction, including lateral spreading, in a simplified

    way. Kinematic soil-pile interaction and inertia soil-pile-structure interaction are considered. Specific

    countermeasures are proposed, such as construction of jet-grouted piles suitably arranged between the

    piles of some of the bridge piers.

    INTRODUCTION

    The examined case study refers to a major highway bridge of almost 1 km long, located at the

    Northeastern part of Greece. The region where the examined bridge is located is almost flat with a light

    bilateral inclination ranging from 0.5% to 1.5% towards Nestos riverbed. The above highway bridgeconsists of two independent branches. The total length of each branch is of 952 m and it consists of

    1 Institute of Engineering Seismology & Earthquake Engineering (ITSAK), 46, Georgikis Scholis str.,

    P.O. Box 53, GR-55102, Finikas, Thessaloniki, GREECE ([email protected], [email protected])2 National Technical University of Athens (NTUA), 9, Heroon Polytechniou Str., Zografou GR-15780,

    GREECE; [email protected] .

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    twenty spans, with the central spans being 65 m, 120 m, and 65 m long. A section of the central part of the

    bridge over the riverbed is sketched in Figure 1.

    The subsoil consists of clean and silty sands, of loose to medium density, with thin layers or interlayers of

    sand-gravel mixture or siltysandy clays, overlaying a good quality gneissic bedrock. It is prone to

    liquefaction under strong seismic motion. An integrated liquefaction risk analysis based on semi-empirical

    methodologies (CPT, SPT, and VS), and also on theoretical results from 1D equivalent linear and non

    linear effective stress analyses in an attempt to account for seismic site response. A cautious combination

    of theoretical and semi-empirical results allows the assignment of a well determined liquefiable zone with

    a high degree of confidence.

    As for the consequences of the liquefied zone on foundation piles, according to the current state of art and

    practice, it is widely accepted that a universal accurate solution, referring to seismic motion of a complex

    system, such as: soil pile group pier bridge under conditions of liquefaction and lateral spreading, is

    rather unlikely to exist. However, due to Kobe earthquake (1995) experience, simplified methods of

    analyses have been proposed in the framework of recent Japanese Earthquake Resistant Design Codes [1].

    A characteristic feature of the above simplified analyses is dissociation of pre- and post liquefaction

    stages.

    Figure 1. A section of the bridge including the 120 m long, central span over the riverbed.

    SITE CHARACTERIZATION AND LIQUEFACTION SUSCEPTIBILITY

    The general geology of the broad area consists of Pleistocenic sediments (gravel, coarse sand and

    moraine) and semi-consolidated pleistocenic sediments (cemented gravel and sands).

    At the study area where the bridge is scheduled to be founded, soil materials are distinguished as follows:

    M5 M6 M7

    RDg

    ALsALs

    ALs

    gngn

    LIQUEFIABLE

    ZONE

    riverbed deposits

    0 100 m

    M5M5 M6M6 M7M7

    RDg

    ALsALs

    ALs

    gngn

    LIQUEFIABLE

    ZONE

    riverbed deposits

    0 100 m0 100 m

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    River deposits (RD) of river Nestos consisting of sands, silty and clayey silty sands, gravels and

    occasionally pebbles of gneiss or marble.

    Alluvial deposits (AD) essentially of sandy nature, with fluctuating percentage of clays, silts and

    gravels. Occasionally, thin layers of gravels and clays / silts are encountered. According to

    geotechnical investigation programs carried out for this area, alluvial deposits are of considerable

    thickness ranging from 12 to almost 55m. Those layers are relatively loose and considerably

    uneven, and in some cases an increased percentage of organics has been detected.

    The bedrock consists mainly of biotitic gneiss (gn) locally interpolated by amphibolites and marbles of

    gray green colour. Sedimentary layers become thicker and more cohesive or dense with depth. Free

    ground water level is normally located at a depth ranging from 1.5 to 6.0m below ground surface and the

    pore water pressure is hydrostatic from this level.

    Based on geotechnical investigation the under study area, of almost 1 Km length, can be divided into three

    major regions, if physical, mechanical and dynamic characteristics of different soil layers are carefully

    combined. In the present work the most representative profile I, in terms of liquefaction susceptibility,

    corresponding to the central spans of the bridge is used for seismic analysis purposes and is presented in

    Figure 2.

    55

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    0 400 800 1200

    VS(m/s)

    55

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    5

    0

    18 20 22 24 26

    Unit Weight (KN/m3)

    55

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    0-3.0

    GPSP

    SP

    SM

    SP

    WZ

    WR

    Loose to mediumdense, poorly graded

    sandy gravels andmedium grained

    poorly graded Sand

    Loose-mediumdense

    fine-grainedpoorly graded SAND

    Medium densesilty sand

    with gravels (~15%)

    Medium dense todense medium grained

    poorly gradedSAND

    (silty sand &gravels, locally)

    Weathered zone

    of gneiss

    Weathered Gneiss

    Dr(%)

    50

    45

    60

    40

    65

    85

    Uc(d60/d10)

    20.0

    12.113.3

    3.0

    5.7

    3.3

    3.3

    50

    K(m/s)

    10-7

    10-7

    10-7

    10-7

    10-8

    10-9

    10-8

    ( )

    33

    36

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    'co/'

    1.5

    1.1

    2.0

    1.0

    4.0

    4.0

    c(kPa)

    0

    0

    0

    0

    0

    0

    el hys mob

    1E-08 1E-04 1E-01

    1E-08 1E-04 1E-01

    1E-08 1E-04 1E-01

    1E-08 1E-04 1E-01

    1E-08 1E-05 1E-01

    1E-08 1E-03 1E-01

    Figure 2. Representative soil profile of the central area (soil profile ) and dynamic properties used

    in effective stress seismic analyses.

    A critical step to start with, is the assignment of soil layers liquefaction susceptibility, by implementation

    of compositional criteria relevant to soil texture, sieve analysis, grain size and physical characteristics.

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    Criteria described as above result from laboratory tests and observations on liquefied soils. Limits of

    sandy soils prone to liquefy according to uniformity coefficient (UC), are proposed in Technical Standards

    for Port and Harbour facilities in Japan [2]. In case of increased percentage of gravels or fines,

    implementation of additional criteria referring to plasticity and water content are applied in order to

    quantify liquefaction susceptibility according to Wang [3], Finn [4] and Andrews [5].

    SITE RESPONSE AND LIQUEFACTION RISK ASSESSMENT

    Nine accelerograms have been considered in this project to describe the excitation at rock outcrop. Based

    on seismic hazard analysis for the area under consideration, the peak ground horizontal acceleration at

    outcropping bedrock conditions was at 0.26g.

    Site response analyses were performed using total and effective stress analyses. Total stress analyses were

    performed with SHAKE [6]. In this paper site response analyses are restricted only to the central area of

    the project, as being the most representative and appropriate for liquefaction risk assessment. Shear

    modulus ratio, G/Gmax, and damping ratio, DS, curves as function of shear strain, were obtain from the

    literature [7], [8], [9,10], [11], [12]), as shown in Figure 3. Non-Linear analyses [13], and effective stress

    analyses using elastoplastic multimechanism model [14], [15], [16,17] and the reduced-order bounding

    hypoplasticity model [18, 19] were also performed.

    0.0001 0.001 0.01 0.1 1 10

    Shear Strain, (%)

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    G/G

    max

    0.0

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0

    G/G

    max

    1. Ishibashi & Zhang (1993) ' = 50 kPa2. Ishibashi & Zhang (1993) ' = 100 kPa3. Ishibashi & Zhang (1993) ' = 200 kPa4. Ishibashi & Zhang (1993) ' = 300 kPa5. Ishibashi & Zhang (1993) ' = 400 kPa6. Ishibashi & Zhang (1993) ' = 500 kPa7. Anastasiadis (1994) Stiff sandy Clay with gravels8. Hatanaka et al. (1995) Sandgravels9. Vucetic & Dobry (1991) Clay PI=010. Vucetic & Dobry (1991) Clay PI=1511. Pitilakis et al. (1998) Sand (SP, SM)12. Pitilakis et al. (1998) Weathered Rock13. Idriss (1972) Rock

    0.0001 0.001 0.01 0.1 1 10

    Shear St rain, (%)

    0.0

    5.0

    10.0

    15.0

    20.0

    25.0

    30.0

    0.0

    5.0

    10.0

    15.0

    20.0

    25.0

    30.0

    DS

    (%)

    1. Ishibashi & Zhang (1993) ' = 50 kPa2. Ishibashi & Zhang (1993) ' = 100 kPa3. Ishibashi & Zhang (1993) ' = 200 kPa4. Ishibashi & Zhang (1993) ' = 300 kPa5. Ishibashi & Zhang (1993) ' = 400 kPa6. Ishibashi & Zhang (1993) ' = 500 kPa7. Anastasiadis (1994) Stiff sandy Clay with gravels8. Hatanaka et al. (1995) Sandgravels9. V ucetic & Dobry (1991) Clay PI=010. Vucetic & Dobry (1991) Clay PI=1511. Pitilakis et al. (1998) Sand (SP, SM)12. Pitilakis et al. (1998) Weathered Rock13. Idriss (1972) Rock

    Figure 3. Variation of shear modulus (G/Gmax) and damping ratio (DS) with shear strain (%):

    curves from literature used in seismic response analyses (equivalent linear).

    Comparison of peak acceleration, shear strain and stress values obtained from total and effective stress

    analyses is portrayed in Figure 4. For the majority of input motion accelerograms, shear strains calculated

    with equivalentlinear methodology appear to be rather unrealistically high. On the other hand, some ofthe inelastic methods of analysis may be somewhat unsafe in leading to reduced amplitudes of

    acceleration. It is believed that reality lies somewhere in between.

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    55

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    5

    00.1 0.2 0.3 0.4 0.5 0.6

    max Acceleration (g's)

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    0

    0 0.2 0.4 0.6 0.8 1

    max Shear Strain (%)

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    0-3.0

    GPSP

    SP

    SM

    SP

    WZ

    WR

    0 50 100 150 200 250

    Shear Stress (kPa)

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    0

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    0

    KAL-DecAigrockPacoima-NSShinkobe-NS

    Non-Linearanalyses

    EquivalentLinear analyses

    Figure 4. Soil Profile I - Peak accelerations, shear strains and stresses : confrontation of results

    from non-linear (solid lines) and equivalent linear (dashed lines) analyses with 4 input motions.

    Highly non-linear behavior of loose clean-sandy layers is depicted in calculated excess pore water pressure

    ratio time histories (Figure 5a) indicating high liquefaction risk. Maximum pore water pressure variation

    with depth is shown in Figure 5b. It is easily shown that the zone of high pore water pressure in excess of

    80% extends from 5 to 16m below free ground surface and also another zone is delimited between 22 and

    32m. It is then theoretically concluded that liquefaction risk is very high at the aforementioned depths.

    Despite theoretical results for the deeper zone, we cannot convincingly argue that liquefaction will occur

    for depths exceeding 25 m to 30 m since almost no evidence of liquefaction at such depths exists.

    Response spectra resulting from total and effective stress analyses are presented in Figure 6 and exhibit

    relatively high values at periods between 0.2 and 0.8 sec and to some extent up to 1.2 sec.

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    0

    0.2

    0.4

    0.6

    0.8

    1

    u/'v0

    -25.5 m-16.0-14.0-22.5

    -20.0-12.0

    0 5 10 15 20 25 30Time (sec)

    -3-2

    -10123

    acc.

    (m/s2)

    Input Motion: KAL86-dec. 0.26g

    3 6.0 4 8.0 5 10.0 6 12.0 7 14.0 8 16.0 9 18.0 10 20.0 11 22.5 12 25.5 13 29.0

    Soil MeanLayer Depth(m)

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    0 200 400 600 800

    Pore-Pressure (Over) (kPa)

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    0-3.0

    GPSP

    SP

    SM

    SP

    WZ

    WR

    'VO

    1 sec4 sec6 sec10 sec

    KAL-D

    Figure 5. Soil Profile I - Effective stress analysis: (a) Calculated excess pore water pressure ratio

    time histories at various depths and (b) maximum pore water pressure variation with depth.

    Elastic Acceleration Response Spectra at free Surface Soil Model

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

    1.4

    1.6

    1.8

    2.0

    2.2

    2.4

    2.6

    0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

    T : sec

    Sa

    :g

    Aigio-DKalam-D

    Kozani-TArgost83-1LKEDE-DShinkobe-NSTemplorPacoima-EWPacoima-NSKAL-H NLAIGIO-H NLShink-H-NLPaco-NS-H-NLKozani-TArgost83-1L

    Elastic Acceleration Response Spectra at free Surface Soil Model

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

    1.4

    1.6

    1.8

    2.0

    2.2

    2.4

    2.6

    0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

    T : sec

    Sa

    :g

    Aigio-DKalam-D

    Kozani-TArgost83-1LKEDE-DShinkobe-NSTemplorPacoima-EWPacoima-NSKAL-H NLAIGIO-H NLShink-H-NLPaco-NS-H-NLKozani-TArgost83-1LKEDE-DTemplorPacoima-EWAver.Aver.+1SDAver.-1SDPROPOSED

    Figure 6. Elastic acceleration response spectra at free ground surface (Soil Profile I): synthesis of

    total and effective stress analyses results.

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    Mean elastic acceleration response spectrum one standard deviation (m +) is also included in Figure 6.

    The design peak ground horizontal acceleration adopted for this case study is 0.36g, mainly based on

    theoretical results of non-linear and effective stress analyses.

    Evaluation of liquefaction risk was based on results of theoretical analyses and selected semi-empirical

    methodologies, with emphasis on stressbased procedures. More specifically, the amplitude of

    earthquake-induced demand (quantified by cyclic stress ratio parameter CSR) was determined using

    simplified relation-ships and peak ground horizontal design acceleration values, and also from results of

    theoretical analyses. The soil strength against liquefaction (quantified as a function of the cyclic resistance

    ratio CRR) was determined by empirical relationships provided in EC8 [12], NCEER 97 13] based on

    field data such as: SPT, CPT and Vs. Figures 7 and 8, based on a characteristic borehole and static

    penetrometer borehole, show synthetical results of semi-empirical methodologies applied to assess factors

    of safety against liquefaction (FSL) and an accurate, as possible, description and evaluation of liquefaction

    risk.

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    0

    3.9

    3.9

    3.9

    3.9

    4.1

    4.1

    4.1

    4.1

    29.2

    29.2

    29.2

    29.2

    1.3

    1.3

    1.3

    1.3

    1.3

    1.3

    1.3

    Log 0 10 20 30 40 50

    N-(S.P.T.) (N1)60CS

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    5

    0

    14

    19

    22

    19

    13

    19

    31

    34

    30

    0 0.2 0.4 0.6 0.8

    Cyclic Resistance RatioCRR7.5

    30

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    10

    5

    0

    0 0.2 0.4 0.6 0.8

    Cyclic Stress RatioCSR

    30

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    10

    5

    0

    0 1 2 3 4

    Factor of SafetyFSL - =7

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    0

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    25

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    10

    5

    0

    -4.20

    EC-8NCEER 98

    E.L.A.-max

    E.L.A.-rd,=0.379g

    EC-8 -=0.260gNCEER 98-=0.260g

    E.L.A.-max

    E.L.A.-r d ,=0.379g

    EC-8 -=0.260gNCEER 98-=0.260g

    GPSP

    SP

    Liquefaction

    Risk

    SM

    SPSM

    Liquefaction"Susceptibility"

    based onCompositional

    criteria

    Figure 7. Implementation of various methodologies for estimating cyclic resistance ratio (CSR) and

    safety of factor against liquefaction (FSL) from SPT tests.

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    The calculated factors of safety against liquefaction, based on SPT values, specify zones presenting a high

    risk to liquefy. For the above borehole the high risk zone for liquefaction to occur ranges from 11 to 25 m

    of depth. The estimated risk is slightly reduced between 17 and 20 m. The bullets of red, yellow and black

    color are indicative of liquefaction susceptibility (Red color: high susceptibility, yellow color: medium

    susceptibility, green color: small susceptibility and black color: refers to soil sample not prone to

    liquefy).

    The CPT based factors of safety against liquefaction delimit a more extended zone of medium high to

    high risk of liquefaction from 7 to 25 m. They differ slightly from the SPT based factor. Those differences

    are deemed justified, since SPT measurements are relatively sparsed (every 2 to 2.5m), compared to CPT

    values registered every 0.2m, as shown in Figure 8.

    30

    25

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    5

    0LOG

    7

    5878

    9

    8

    9

    5

    9898

    9

    89

    8

    9

    8

    9

    0 20 40

    qC(MPa)

    30

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    15

    10

    5

    00 0.2 0.4 0.6 0.8

    CRR7.5

    0 0.2 0.4 0.6 0.8

    CSR

    NLIQ

    NLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQNLIQ

    NLIQNLIQNLIQ

    NLIQ

    0 1 2 3 4 5

    Factor of SafetyFSL - =7

    30

    25

    20

    15

    10

    5

    0

    30

    25

    20

    15

    10

    5

    0

    -4.

    E.L.A.- maxE.L.A.-r d ,=0.379g

    EC-8 - =0.260gNCEER 98- =0.260g

    0 2 4 6

    fr (%)

    0 1 2 3 4

    IC

    0 40 80

    FC (%)

    0 200 400

    qc1,cs

    1 Sensitive fine grained2 Organic material3 Clay4 Silty clay to clay5 Clayey silt to silty clay6 Sandy silt to clayey silt

    7 Silty sand to silty clay8 Sand to silty sand9 Sand10 Gravelly sand to sand11 Very stiff grained (OC or Cem.)12 Sand to clayey sand (OC or Cem.)

    SieveAnalysis

    Liquefaction

    Risk

    Ic=2.6

    E.L.A.-max

    E.L.A.-rd,=0.379g

    EC-8 -=0.260gNCEER 96-=0.260g NCEER 98- CPT& E.L.A.-

    max

    EC-8Seed et al.(1986)Ishihara (1985)Rob.&Camp.(1985)NCEER-98- Vs NCEER-98- CPT

    -4.20

    Robertson,1

    986 EC-8

    Seed et al.(1986) NCEER-98- CPT

    Figure 8. Implementation of various methodologies for estimating cyclic resistance ratio (CSR) and

    factor of safety against liquefaction (FSL) from CPT and Cross-Hole tests.

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    The kinematic response of the soil-pile system after excess pore water pressures arise is subdivided into

    two distinct stages of response:

    Stage A, when considerable pore water pressures have developed ( vou > 50.0 ) but no

    widespread liquefaction has yet occurred. At this stage, the soil reaction to pile is drastically

    reduced, but it still preserves a non-zero shear stiffness so that seismic waves can propagate

    through and affect the pile. Thus, the nature of pile response is still predominantly dynamic but is

    also significantly different from a linear or moderately nonlinear behavior.

    Stage B, which takes place after the earthquake loading has ended. Now, lateral spreading of the

    liquefied soil may take place under certain conditions, such as an inclination of the soil layers or

    the surface resulting in a quasi-static, gravity-induced loading to the pile. Static analysis can be

    performed to estimate the pile response by imposing a displacement loading along the supports of

    springs connecting soil and pile; no inertial loading from the superstructure applies.

    The analysis of the soil-pile system in the realm of a limited pore water pressure build-up (stage A) is

    based on the procedure adopted by the conventional soil-pile interaction analysis. However, in this casequite softer Winkler soil springs along the pile account for the soil nonlinearities arising in the vicinity

    of the pile. In the Nestos Bridge case, the calibrated distributed springs are portrayed in Figure 9.

    Figure 9. Shear wave velocity and winkler springs distribution with depth for the soil-pile

    interaction analysis. The Vsprofile at low strains is applied for the equivalent non-linear case where

    no liquefaction is accounted for.

    The numerical analysis of the pile response under earthquake motion is performed through the semi-

    analytic algorithm SPIAB (Soil-Pile Interaction analysis for bridge piers, Mylonakis and Gazetas,

    Gerolymos et al 1999). At this stage, inertia loading to pile is negligible due to strongly reduced

    acceleration levels, thus a kinematic interaction analysis is adequate to predict the total system response.

    0

    5

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    2025

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    40

    0 200 400 600 800 1000

    Vs [m/s]

    z

    [m]

    Vs design profile withliquefaction

    Vs profile at low strains

    0

    5

    10

    15

    20

    25

    30

    35

    40

    1 10 100 1000

    kH[MPa/m]

    z[m]

    (a) shear wave velocity (b) Winkler soil springs

    SOILPILE STRUCTURE INTERACTION IN LIQUEFIABLE SOIL

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    The time history of the Pacoima dam recorded in the Northridge 1994 earthquake is used as excitation at

    outcropping bedrock, after scaling down to 0.26 g to be compatible to the Greek code provisions (see

    Figure 10).

    Figure 10. The acceleration time-history and response spectrum at 5% damping ratio of the scaled

    Pacoima dam record.

    The results are plotted in Figure 11 for a 40 m long pile in terms of bending moment and shear force

    distributions. The results of the moderately nonlinear case which does not account for any pore-pressure

    built-up are also plotted in this figure. It is clear that the slightly liquefied soil has a strongly detrimentaleffect on the response. The magnitude of the bending moment below the pile cap (z = 0) increases to 2800

    kNm, which is nearly double the no-liquefaction value. Furthermore, the shear force is even more

    amplified reaching about 480 kN at the depth of 10 m. The detrimental effect of pore-pressure

    development is mainly the outcome of strongly amplified free-field shear deformations due to soil

    softening; this overshadows the beneficial reduction of Winkler spring stiffness.

    Figure 11. Bending moments and shear forces along the pile for the case of slightly liquefiable soil in

    comparison with the moderately nonlinear response without pore-pressures built up.

    The lateral spreading potential of the liquefiable soil is of rather minor importance, regarding that the

    liquefiable layers and ground surface extend almost horizontally. A possible exception to the general case

    involves the two piers M6 and M7 of the central span (see Figure 1) where a slight increasing of ground

    surface inclination is possible due to a future erosion of the riverbed deposits. For these piers, specific

    countermeasures are proposed to prevent any additional loading to the piles after lateral spreading onset.

    0

    0.5

    1

    1.5

    0 0.5 1 1.5 2

    T : s

    Sa:g

    -0.4

    -0.2

    0.0

    0.2

    0.4

    0 2 4 6 8 10

    t [s]

    a

    [g]

    0

    5

    10

    15

    20

    25

    30

    35

    40

    45

    0 100 200 300 400 500

    Q: kN

    z:m

    kh,min

    kh,liq

    0

    5

    10

    15

    20

    25

    30

    35

    40

    45

    0 500 1000 1500 2000 2500 3000

    M [kNm]

    z[m]

    kh,min

    kh,liq

    no liquefaction

    slightly

    liquefied

    no liquefaction

    slightly

    liquefied

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    Such measures include the construction of 0.8 m diameter jet-grouted piles suitably arranged between the

    piles. The configuration of ground improvement for the pier M6 case is sketched in Figure 12.

    Figure 12. Configuration of the stone columns for the pier M6 case.

    ACKNOWLEDGEMENTS

    The work was conducted with the support of the Egnatia Odos Company.

    REFERENCES

    1. JSCE. Earthquake Resistant Design Codes in Japan. Japan Society of Civil Engineers, 2000.

    2. Technical Standards for port & harbour facilities in Japan from Handbook and Liquefaction

    Remediation of Reclaimed Land, Edited by Port & Harbour Res. Inst. Balkema, 1997.

    3. Wang, W. Some findings in soil liquefaction, Water Conservancy and Hydroelectric Power

    Scientific Research Institute, 1979, Beijing, China.

    4. Finn, W.D.L., Ledbetter, R.H., and Wu. G. Liquefaction in Silty Soils: Design and Analysis, 1994,

    Ground Failures under Seismic Conditions, Geotechnical Special Publication No.107, ASCE.

    5. Andrews, D.C.A. and Martin, G.R. Criteria for Liquefaction of Silty Soils.12th

    World Conference

    on Earthquake Engineering, 2000, Proc., Auckland, New Zealand.

    6. Schnabel P.B., Lysmer J. and Seed H.B. SHAKE: A computer program for earthquake responseanalysis of horizontally layered sites, Report No. UCB/EERC-72/12, 1972, Earthquake Engineering

    Research Center, University of California, Berkeley, December, 102p.

    7. Ishibashi, I. And Zhang, X. Unified dynamic shear moduli and damping ratios of sand and clay,

    Soils and Foundations, 1993, Vol. 33, No 1, pp.182-191.

    8. Anastasiadis, A.J. Contribution to the determination of the dynamic properties of natural Greek

    soils, Ph.D. Thesis (in Greek), 1994, Dep. of Civil Engineering, Arist. University of Thessaloniki.

    9. Hatanaka M. and Uchida A. Effects of test methods on the cyclic deformation characteristics of high

    pile 150

    22.0 m

    30.0m

    15 m 3.0 m

    stone columns 80

  • 8/10/2019 Literature on Lquefaction

    12/12

    quality undisturbed gravel samples. Statics and dynamic properties of gravelly soils, 1995, ASCE,

    Geotechnical special publication, No.56, pp.136-151.

    10. Hatanaka N., Suzuki Y., Kawasaki T. and Endoh M. Cyclic undrained shear properties of high

    quality undisturbed gravel, 1988, Soils and Foundations, Vol.28, No.4, J. of JSSMFE, pp.57-68.

    11. Vucetic, M., and Dobry, R. Effect of Soil Plasticity on Cyclic Response. Journal of the Soil

    Mechanics and Foundations Division, ASCE, 1991, Vol. 117, No. 1, pp.89-107.

    12. Pitilakis K., Raptakis D., Lontzetidis K., Tika Th. And Jongmans D. Geotechnical and geophysical

    description of EURO-SEISTEST using field, laboratory tests and moderate strong-motion

    recordings. Journal of Earthquake Engineering, 1999, 3(3), pp. 381-409.

    13. Gerolymos N. and Gazetas G. Constitutive model for 1-D cyclic soil behaviour applied to seismic

    analysis of layered deposits, Soils & Foundations 2004 (in press)

    14. Aubry D., Hujeux J.C., Lassoudire F. And Meimon Y. A double memory model with multiple

    mechanisms for cyclic soil behaviour. Int.Symp. Num.Mod.Geomech., 1982, Balkema, 3-13.

    15. Hujeux, J.C. Une loi de comportement pour les chargements cycliques des sols. Genie

    Parasismique (Davidovici, ed.), 1985, Presses ENPC, Paris.

    16. Modaressi, H., E. Foerster and A. Mellal. Computer-aided seismic analysis of soils, Proc.6th

    Symp.On Num. Models in Geomech., 1997, Canada, pp.427-432.

    17. Modaressi A. and F.Lopez-Caballero. Global Methodology for Soil Behavior Identification and its

    Application to the Study of Site Effects. Proc.4th

    Int.Conf. on Recent Advances in Geotechnical

    Earthquake Engineering and Soil Dynamics, 2001, March 26-31, San Diego, California.

    18. Li X.S, Wang Z.L.and C.K. Shen. SUMDES: A Nonlinear Procedure for Response Analysis of

    Horizontally-layered Sites Subjected to Multi-directional Earthquake Loading, Department of Civil

    Engineering, 1992, University of California, Davis.

    19. Li X.S., Dafalias Y.F. and Wang Z.L. A critical-state hypoplasticity sand model with state dependent

    dilatancy. Can.Geotech.J., 1999, Vol.36, No.4, pp.587-598.

    20. EC8 (2002), Design Provisions for Earthquake Resistance of Structures, Part 1-1: General Rules-

    Seismic Actions and General Requirements for Structures (draft), pren 1998-5, Eur. Committee for

    Standardization, Brussels.

    21. NCEER (1997). Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of

    Soils, (T.L.Youd and I.M. Idriss, eds.), Technical Report NCEER-97-0022, National Center forEarthquake Engineering Research, State University of New York at Buffalo, 276pp.

    22. Seed, H.B. and De Alba P. Use of SPT and CPT tests for evaluating the liquefaction resistance of

    soils, 1986, Proc., Insitu86, ASCE.

    23. Seed, .., and I.M.Idriss Simplified Procedure for Evaluating Soil Liquefaction Potential, Journal

    of the Soil Mechanics and Foundations Division, 1971, 97(SM9), pp.1249-1273.

    24. Ishihara K. Stability of natural deposits during earthquakes, In Proc., 11th

    Intern.Conf.on Soil

    Mechanics and Foundation Engineering, 1985, Vol.1, pp.321-376.

    25. Berrill J., & Yasuda S., (2002), Liquefaction and Piled Foundations: Some Issues, Journal of

    Earthquake Engineering, Special Issue 1, Vol. 6, pp. 1-41.

    26. Dobry R., & Abdoun T., (2001), Recent Studies on Seismic Centrifuge Modeling of Liquefaction

    and its Effect on Deep Foundations, SOA Paper, Proceedings of the Fourth International Conference

    on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics (S. Prakash, ed.),San Diego, CA, pp. 26-31.

    27. Gazetas G. & Mylonakis G. (1998), Seismic Soil-Structure Interaction : New Evidence and

    Emerging Issues, Soil Dynamics III, American Society of Civil Engineers, (ASCE), Specialty

    Geotechnical Conference, Seattle, Vol. 2, p.p. 1119-1174.

    28. Ishihara K., & Cubrinovski M., (1998), Problems Associated with Liquefaction and Lateral

    Spreading during Earthquakes, Soil Dynamics III, American Society of Civil Engineers, (ASCE),

    Specialty Geotechnical Conference, Seattle Vol. 1 pp. 301-312.