RECONSIDERATION OF INITIATION OF LIQUEFACTION IN SANDY SOILS

The Berkeley trigger criterion for evaluating the potential for earthquake-induced phenomena in sandy soils is reviewed in this paper. The historical database comprising the criterion is reconsidered using a consistent ''weakest-link-in-the-chain'' approach. Revised plots of average cyclic stress ratio (CSR) versus (N-l)(60) are presented using the new minimum values of (N-1)(60). Lower-bound state lines, in terms of (N-l)(60), are applied to the nonliquefied data and upper-bound state lines are applied to the liquefied data. It is found that these lines do not coincide, forming a single trigger line in either clean sand or sand with fines; instead, they define a zone in which liquefaction may or may not occur. An additional zone is defined in which earthquake-induced phenomena are likely to consist of only sand boils. This supports the necessity of site-specific investigations to determine liquefaction potential. The results of this study demonstrate the effect of fines content on liquefaction potential, but not to the same extent as found in original interpretations of the field data.