Soil Liquefaction Screening Using CPT Yield Stress Profiles

A novel approach to screen for soil liquefaction potential utilizes the stress history profile obtained from cone penetration tests (CPT) to differentiate contractive versus dilative behavior within the context of critical state soil mechanics (CSSM). Contractive soils are liquefaction prone, whereas dilative soils are not. Specifically, the profiles of apparent yield stress (σp') and yield stress ratio (YSR) with depth are determined from the net cone resistance (qnet) and CPT material index (Ic) from an established relationship for sands, silts, and clays. When the in situ YSR falls below a threshold value established by CSSM (i.e., YSR<3), the soil is contractive, whereas otherwise it is dilative. Both static flow and cyclic liquefaction can be assessed in this manner. Four case studies showing the YSR triggering threshold are shown in comparison with standard procedures.