A Site-Specific Comparison of Simplified Procedures for Evaluating Cyclic Resistance of Non-Plastic Silt

Abstract

Assessing the liquefaction potential of silts is a challenging problem for practicing engineers. A common approach to performing such assessments is to apply a fines content correction factor to field-based correlations that were developed primarily for sands that relate cyclic resistance and in-situ indices (i.e., standard penetration test (SPT) N-value, cone penetration test (CPT) qc-value, or shear wave velocity (VS)). This paper compares the cyclic resistance estimated using these methods for a site in Providence, Rhode Island which is characterized by deep deposits of non-plastic silt. Standard penetration tests with energy measurements were performed in conjunction with seismic cone penetration tests, and representative samples were collected for laboratory testing. A site-specific VS-based cyclic resistance correlation was developed from cyclic triaxial tests with shear wave velocity measurements and was used as a baseline for comparing the results of current SPT- and CPT-based simplified approaches. The analysis suggests that the existing SPT- and CPT-based methods, as described in Youd et al. (2001), provide reasonable predictions of cyclic resistance of the non-plastic silt when the recommended fines content corrections are applied.