Evaluation and Use of Residual Strength in Seismic Safety Analysis of Embankments

Abstract

A reevaluation of the performance of the Lower San Fernando Dam during the February 9, 1971 San Fernando earthquake was conducted to evaluate methods of determining the residual shear strengths of liquefied soils. The use of Standard Penetration Test (SPT) N-value correlations, as proposed by H. B. Seed and his colleagues at the University of California, and laboratory tests to obtain steady-state strength as proposed by Gonzalo Castro and his colleagues at GEI, Inc., are evaluated. A recommended approach for seismic safety analysis is presented. The approach, which is intended for use by practicing engineers and not for problems of a research nature, generally consists of the techniques developed by Seed and his colleagues and incorporates routine use of a field performance-based correlation between soil strength and SPT blow counts.