Jin-Hung Hwang National Central University, Taiwan

1. U.S.-Taiwan Workshop on Soil LiquefactionA Practical Reliability-Based Method for Assessing Soil Liquefaction Potential Jin-Hung Hwang National Central University, Taiwan

2. Outline Previous studies Reliability model Probability density function of CSR Probability density function of CRR Liquefaction probability and safety factor Summary and discussion

3. 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)

4. 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.

5. Reliability Model • Based on Seed’85 method • Assume CSR and CRR are normal distribution

6. Fig.1 Probability density distribution for the liquefaction performance function.

7. Assume CSR and CRR are log-normal distributions

8. Flow chart of calculation

9. Information required • Mean values and variance coefficients of CSR and CRR Table 2 Mean values and variance coefficients of CSR and CRR

10. PDF of CSR Fig.2 Calculated probability density function of a soil at a depth of 10 m.

11. PDF of CRR Table 1 Parameters in the logistic model Fig.3 Probabilistic cyclic resistance curves regressed by the logistic model.

12. PDF of CRR Fig.4 Probability density function of the soil cyclic resistance ratio.

13. PDF of CRR Fig.5 Mean and median curves compared with the probabilistic curve of PL=0.6.

14. Liquefaction Probability and Safety Factor Fig.7 Relations of liquefaction probability with the safety factor for different variance coefficients.

15. 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.

16. Compared with Juang’s result Fig.9 Relation of liquefaction probability with the safety factor calculated by Seed’85 method.

17. Parameter Study • Influences of and the ground water table on the liquefaction probability Fig.10(a) Variation of liquefaction probability with (N1)60.

18. Parameter Study • Influences of and the ground water table on the liquefaction probability Fig.10(b) Influence of fines content on liquefaction probability.

19. Parameter Study • Influences of and the ground water table on the liquefaction probability Fig.10(c) Influence of ground water table on liquefaction probability.

20. Application Example • Active Hsinhwa fault (12km rupture) • 1946 Tainan earthquake • Caused extensive liquefaction • Design earthquake • Result of liquefaction analysis

21. Application Example Table 3 Result of liquefaction analysis for the site near the Hsinhwa fault

22. Application Example Fig.11 Result of liquefaction analysis for the site near the Hsinhwa fault.

23. 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