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Transcript of Residual shear strength of liquefied Response/Boulanger_TRB_2007.pdfآ  Residual shear strength of...

  • 1

    University of California, Davis Department of Civil & Environmental Engineering

    Residual shear strength of liquefied soils

    Ross W. BoulangerTRB 2007

    Lab testing of field samples:

    Frozen sampling techniques (e.g., Robertson et al. 2000)

    T b li ith ti ( C t 1975 P l t l 1985)

    Evolution of procedures for estimating Sr

    Tube sampling with corrections (e.g., Castro 1975, Poulos et al. 1985)

    Case history based correlations

    Back-analyses of flow slide failures

    Initially by Seed (1987); modifications & updates by others (e.g., Seed & Harder 1990, Wride et al. 1999, Olson & Stark 2002)

    Void redistribution

    Articulated by Whitman (1985); advances by physical & analytical modeling (e.g., Kokusho 2000, Kulasingam et al. 2004, Malvick et al. 2004, Naesgaard et al. 2006)

    Seed (1987) noted that case history based correlations implicitly account for void redistribution

  • 2

    Recommend relationships for Sr /σ'vo based on reviews of:

    Case history studies

    This presentation

    Laboratory testing studies

    Void redistribution studies

    Emphasis on providing rational guidance for extrapolation beyond case history data.

    Idriss & Boulanger (2007). "Residual shear strength of liquefied th SSsoils," 27th USSD Annual Meeting, March. Preprint at:

    http://cee.engr.ucdavis.edu/faculty/boulanger/PDFs/2007/Idriss_Boulanger_USSD_2007_preprint.pdf

    Back-analysis

    Post-earthquake stability analysis:

    Upper bound Sr from undeformed geometry

    Lower bound S from final deformed geometryLower bound Sr from final deformed geometry

    Interpolated Sr depends on sliding inertia, evolving geometry, intermixing (soils & water), other factors

    Example: Olson & Stark (2002) results for LSF dam:

    (Sr)upper ≈ 36 kPa

    (Sr)lower ≈ 5 kPa

    (Sr)best ≈ 19 kPa

    (Seed 1987)

  • 3

    Group 1: 7 cases with adequate SPT/CPT & geometric details

    Case histories

    Groups 2 & 3: 11 cases with either adequate SPT/CPT or geometric details, but not both

    Group 4: 17 cases with inadequate details

    Calaveras dam – CA DSOD

    Lower San Fernando dam – CA DSOD

    Case History (N1)60cs-Sr *

    / / FC **

    Residual Strength, Sr (kPa) published by σ'vo

    (kPa)***Number Structure Seed (1987) Seed &

    Harder (1990) Olson & Stark (2002)

    1 Wachusett Dam – North Dike --/--/7 5–10 / 5 -- -- 16.0 151.2

    2 Lower San Fernando Dam 15/13.5/11.5 5–90 / 25 35.9 19.2 18.7 166.7

    3 Fort Peck Dam 11/10/8.5 55 / 50 28.7 16.8 27.3 351.5

    Published case histories of liquefaction flow failures

    4 Calaveras Dam 12/12/8 10–>60 / 60 35.9 31.1 34.5 307.5

    5 Hachiro-Gata Road Embankment --/--/4.4 10–20 / 15 -- -- 2.0 32.1

    6 Lake Ackerman Highway Embankment† --/--/3 0–5 / 0 -- -- 3.9 51.5

    7 Route 272 at Higashiarckinai --/--/6.3 20 / 20 -- -- 4.8 49.3

    8 River Bank, Lake Merced 5/6/7.5 1–4 / 3 4.8 4.8 6.9 65.7

    9 Kawagishi-cho 4/4/4.4 0–60–85 / 85 12.0 12.0 5.4 52.2

    11 La Marquesa Dam – U/S Slope †† --/6/4.5 30 /30 -- 9.6 3.1 43.6

    12 La Marquesa Dam – D/S Slope ††† --/11/9 20 / 20 -- 19.2 5.3 47.9

    13 l /4/3 1 / 1 9 6 4 8 3 813 La Palma Dam †††† --/4/3.5 15 / 15 -- 9.6 4.8 37.8

    14 Uetsu Railway Embankment 3/3/3 0–2 / 2 1.7 1.9 1.7 61.3

    15 Solfatara Canal Dike 5/4/4

  • 4

    Values of Δ(N1)60-Sr recommended by Seed (1987)

    Fines Content, FC (% passing No. 200 sieve) Δ(N1)60-Sr

    10 1 25 2 50 4 75 575 5

    0.4

    Correlation of Sr /σ'vo to (N1)60cs-Sr

    Group 2 & Group 3 (see text for more details)

    Group 1 -- Case histories with an adequate amount of in-situ measurements (e.g., SPT, CPT) and reasonably complete geometric details

    Seed (1978)

    Seed & Harder (1990)

    Olson & Stark (2002)

    ar S

    tr en

    gt h

    R at

    io , S

    r/ σ ' vo

    0.2

    0.3

    Recommended Curve for conditions where

    void redistribution effects are expected to be negligible

    Equivalent Clean Sand SPT Corrected Blowcount, (N1)60cs-Sr

    0 5 10 15 20 25 30

    R es

    id ua

    l S he

    a

    0.0

    0.1

    See Figure 4 for Legend

    Recommended Curve for conditions where

    void redistribution effects could be significant

  • 5

    120

    D = 52%

    Vaid & Sivathayalan (1996) Frazer River sand, water pluviated

    Undrained direct simple shear tests σ'vc = 200 kPa

    Undrained stress-strain behavior

    Sh ea

    r S tr

    es s,

    τ (

    kP a)

    40

    80

    DR = 52%

    DR = 43%

    DR = 35%

    DR = 31%

    Shear Strain (%) 0 4 8 12 16 20

    0

    Shear resistance at phase transformation

    R

    vc

    0.6

    Tests with σ'vc = 50, 100, 200 & 400 kPa

    Vaid & Sivathayalan (1996); Vaid et al (1996) Frazer River sand, water pluviated

    Undrained direct simple shear tests 20% shear strain

    Normalized shear resistance

    Sh ea

    r R es

    is ta

    nc e

    R at

    io , τ

    / σ ' v

    0.2

    0.4

    At 20% shear strain

    At phase transformation At 10% shear strain

    At phase transformation vc , ,

    Tests with σ'vc = 200 kPa

    10% shear strain

    Phase transformation

    Relative Density, DR (%) 0 20 40 60 80

    S

    0.0

    These & other results suggest undrained DSS strengths will exceed drained strengths (tanφ' ≈ 0.6) at DR ≥ 50 to 60% for σ'vo ≤ 400 kPa

  • 6

    Sr /σ'vo at QSS relatively independent of σ'vo up to 400 kPa

    Effect of confining stress

    Yoshimine et al. (1999) – QSS strengths

    For σ'vo > 400 kPa, recommend using state corrected N1ξ (Boulanger 2003) rather than N1 in Sr /σ'vo correlations

    yer

    θ φ′pk

    Void Redistribution

    Ht Confin

    ing La yer

    Hb Liquef

    iable L ayer

    Δu

    hd

    hc

    Imperm eable

    Base L ayer

    ru,r @ φ′cv

    Localization if Vcon > Vdil (Boulanger & Truman 1996, Malvick et al. 2006)

    Related studies (Yang and Elgamal 2002, Sento et al. 2004, Yoshimine et al. 2006, Naesgaard et al. 2006)

  • 7

    NEVADA SAND SILT

    Water Surface

    Centrifuge model (Malvick et al. 2004)

    Nevada sand, DR ≈ 35%; 9-m radius centrifuge

    COARSE SAND

    SILT

    0 100 200 mm

    9 m

    7.2 m

    0 4.5 9.0 m

    model scale

    prototype scale

    Pore Pressure Transducer Accelerometer Displacement Transducer

    SILT

    Displacement Transducer

    point point A

    Midslope PPT array

    20

    -20

    0

    0 P9

    P7

    P8

    A B C D E

    0

    0.5

    1

    1.5

    2

    D is

    pl ac

    em en

    t o f

    S lid

    e M

    as s

    (m )

    FED C

    B A

    point C

    12

    16

    ar ra

    y (m

    )

    P P

    Ts

    P6 P7

    P8

    P9

    Silt

    (a) Array 1 Δu in an infinite slope, θ = 18.3° and φ′mob = 33°

    0

    20

    0

    20

    0

    ce ss

    P or

    e P

    re ss

    ur e

    (k P

    a)

    0

    20

    20 P3

    P4

    P5

    P6

    P7 0 400 800

    Time After End of Shaking (s)

    0 2000 2800

    point D

    -10 0 10 20 30 40 50 60 Excess Pore Pressure (kPa)

    0

    4

    8

    P os

    iti on

    a lo

    ng

    P1

    P2

    P3

    P4 P5 P6

    AC BDEF

    0 400 800 1200 1600 Time after end of shaking (s)

    E xc

    0

    0

    20

    0

    20

    40

    P1

    P2

    P3

  • 8

    Role of DR (Kulasingam et al. 2004)

    1-m radius centrifuge tests

    6 4 m high slope

    1.5

    2

    D is

    pl ac

    em en

    t ( m

    ) Motion A Motion B (after A) Motion C (after A & B) Motion C (alone)

    6.4-m high slope (prototype)

    Sand initially dense of critical for all models

    0 20 40 60 80 100 Initial Relative Density (%)

    0

    0.5

    1 In

    cr em

    en ta

    l H or

    iz . D

    Void redistribution summary

    Degree & timing of void redistribution depend on: pre-earthquake soil state (DR, σv′) & properties (cyclic resistance, compressibility), physical geometry (stratigraphy, layer thickness, slope height, slope angle), permeability contrasts, ground motion characteristics (level of shaking, duration).

    With significant void redistribution: Sr /σ'vo is not uniquely correlated to pre-earthquake stater vo Sr /σ'vo can be small as the soil shears and progressively loosens under a net inflow of water and a sustained low value of σ'v

  • 9

    Young NC slightly plastic silts (say PI ≈ 7):

    At transition between soils that should be analyzed using procedures developed for clays versus those for sands

    Slightly plastic silts

    procedures developed for clays vers