Liquefaction Resistance of Sand-Silt Mixtures Using Laboratory-Based Shear Wave Velocity

Laboratory data, which relate the liquefaction resistance of Firoozkooh sand and non-plastic silt mixtures to shear wave velocity are presented and compared to liquefaction criteria derived from seismic field measurements by Andrus and Stokoe [1]. In the work described herein, cyclic triaxial and resonant column tests were conducted on specimens of clean sand and sand-silt mixtures with silt content up to 60%, prepared at different densities. Cyclic undrained strength and small strain shear wave velocity were determined for identical specimens formed by undercompaction method. It was found that silt content affects cyclic resistance and shear wave velocity. In addition, the laboratory results indicated that using the existing field-based correlations will overestimate the cyclic resistance of the Firoozkooh sand-silt mixtures when silt content is 60%. For clean sand and the specimens containing up to 30% fines, results of this study on cyclic resistance are fairly consistent with Andrus and Stokoe correlations. These findings suggest the need for further evaluation of the effects of non-plastic fines content upon liquefaction criteria derived from seismic field measurements.