Liquefaction evaluation indices for fine-grained soils

The methods for estimating soil liquefaction in China were basically established in the 1980s, and they have not substantially improved thence. Following the 1999 Kocaeli and 1999 Chi-Chi Earthquakes, considerable efforts on liquefaction discrimination methods for fine-grained soils have been done by overseas researchers. Referring to previous studies on fine-grained soil liquefaction, indices in SPT-based formula and prelimilary discrimination criteria are specifically analyzed. Reviewing the soil characteristics of liquefaction data from the 1975 Haicheng, 1976 Tangshan, 1999 Kocaeli and Chi-Chi Earthquakes, the advantages and limitations of the existing liquefaction discrimination methods for fine-grained soils are comparatively analyzed. The results show that: (1) Plasticity index should not be used as an index in SPT-based formula. (2) Applying the combination of fine content and clay content to estimate liquefaction potential is more reliable than using either index alone. (3) Chinese code method is much conservative for fine-grained soils, especially considering clay fraction only for the soils with fine content greater than 50%. (4) Clay content should not be used as an index in prelimilary discrimination criteria. (5) The fine-grained soils with plasticity index not less than 10, 13 and 15 corresponding to seismic intensities 7, 8 and 9 respectively will not liquefy.