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A Practical Reliability-Based Method for Assessing Soil Liquefaction Potential

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Lecture Topic: A Practical Reliability-Based Method for Assessing Soil Liquefaction Potential …

Lecture Topic: A Practical Reliability-Based Method for Assessing Soil Liquefaction Potential

By Prof. Jin-Hung Hwang of National Central University, Taiwan.

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  • 1. U.S.-Taiwan Workshop on Soil Liquefaction A Practical Reliability-Based Method for Assessing Soil Liquefaction Potential Jin-Hung Hwang National Central University, Taiwan
  • 2. DATE:10th Nov, 2010 CET Hall
  • 3. www.cesnitsilchar.wordpress.com Fanpage MISSION 2015::NIT Silchar www.twitter.com/cesnitsilchar
  • 4. Outline
    • Previous studies
    • Reliability model
    • Probability density function of CSR
    • Probability density function of CRR
    • Liquefaction probability and safety factor
    • Summary and discussion
  • 5. Previous Studies
    • Haldar and Tang (1975),
    • Fardis and Veneziano (1982),
    • Chameau and Clough (1983),
    • Liao et al . (1988),
    • Youd and Nobel (1997),
    • Toprak et al . (1999) ,
    • Juang et al . (2000a,2000b)
  • 6.
    • Some comments
      • Soil parameters and data should be updated.
      • Probabilistic cyclic strength curves without the statistics.
      • Juang’s work is a notable advancement, however ANN is a little unfamiliar to engineers.
  • 7. Reliability Model
    • Based on Seed’85 method
    • Assume CSR and CRR are normal distribution
  • 8. Fig.1 Probability density distribution for the liquefaction performance function.
  • 9.
    • Assume CSR and CRR are log-normal distributions
  • 10.
    • Flow chart of calculation
  • 11.
    • Information required
      • Mean values and variance coefficients of
      • CSR and CRR
    Table 2 Mean values and variance coefficients of CSR and CRR Mean value Variance coefficient CSR 0.581 CRR 0.604
  • 12. PDF of CSR Fig.2 Calculated probability density function of a soil at a depth of 10 m.
  • 13. PDF of CRR Table 1 Parameters in the logistic model Fig.3 Probabilistic cyclic resistance curves regressed by the logistic model. Parameter β 0 β 1 β 2 β 3 Regressed result 10.4 -0.2283 -0.001927 3.8
  • 14. PDF of CRR Fig.4 Probability density function of the soil cyclic resistance ratio.
  • 15. PDF of CRR Fig.5 Mean and median curves compared with the probabilistic curve of P L =0.6.
  • 16. Liquefaction Probability and Safety Factor Fig.7 Relations of liquefaction probability with the safety factor for different variance coefficients.
  • 17.
    • Compared with the safety factor defined by the Seed’85 method
    Fig.8 Comparison of the probabilistic CRR curves with the empirical curve proposed by Seed’85 method.
  • 18.
    • Compared with Juang’s result
    Fig.9 Relation of liquefaction probability with the safety factor calculated by Seed’85 method.
  • 19. Parameter Study
    • Influences of and the ground water table on the liquefaction probability
    Fig.10(a) Variation of liquefaction probability with (N 1 ) 60 .
  • 20. Parameter Study
    • Influences of and the ground water table on the liquefaction probability
    Fig.10(b) Influence of fines content on liquefaction probability.
  • 21. Parameter Study
    • Influences of and the ground water table on the liquefaction probability
    Fig.10(c) Influence of ground water table on liquefaction probability.
  • 22. Application Example
    • Active Hsinhwa fault (12km rupture)
    • 1946 Tainan earthquake
    • Caused extensive liquefaction
    • Design earthquake
    • Result of liquefaction analysis
  • 23. Application Example Table 3 Result of liquefaction analysis for the site near the Hsinhwa fault depth ( m ) Unit weight ( t / m 3 ) SPT- N FC (%) Soil classification F.S. (Seed) P L (%) 1.3 1.97 3 73 CL-ML - - 2.8 2.02 6 69 CL-ML - - 4.3 2.00 7 75 CL-ML - - 5.8 1.89 15 82 ML - - 7.3 1.93 6 99 ML - - 8.8 2.01 6 91 CL-ML - - 10.3 1.98 17 33 SM 1.2 35% 11.8 1.95 23 29 SM 1.4 19% 13.3 1.87 18 33 SM 1.2 35% 14.8 1.96 13 14 SM 0.8 62% 16.3 1.95 9 99 CL - - 18.8 2.04 33 25 SM 2.0 6% 19.3 2.19 33 20 SM 1.9 9%
  • 24. Application Example Fig.11 Result of liquefaction analysis for the site near the Hsinhwa fault.
  • 25. Summary and Discussion
    • A simple and practical reliability method for liquefaction analysis was proposed
    • The liquefaction probability is just a probability under a given earthquake event
    • It needs to combine the probability of earthquake occurrence