SHEAR WAVE VELOCITY-BASED LIQUEFACTION RESISTANCE OF SAND-SILT MIXTURES: DETERMINISTIC VERSUS PROBABILISTIC APPROACH

Laboratory data that relates the liquefaction resistance of sand and silt mixtures to shear wave velocity are presented and compared to the liquefaction criteria derived from seismic field measurements based on the deterministic and probabilistic methods. In the deterministic method, cyclic triaxial and resonant column tests were conducted on specimens of Firoozkooh clean sand and sand-silt mixtures with a silt content up to 60% at different densities (Dr =15, 30, 60 and 75%). Cyclic undrained strength (CRR) and small strain shear wave velocity were determined for identical specimens formed using the undercompaction method and laboratory results were converted to field and compared to liquefaction criteria derived from seismic field measurements in previous research. In the probabilistic method, the three-sigma rule was used to analyze the uncertainty factors in liquefaction hazard analysis based on laboratory data. Probabilistic diagrams were also compared with that of other researchers. Results show that the use of the existing fieldbased correlations to assess CRR is overestimated in comparison to field cyclic resistance evaluated by laboratory testing for the Firoozkooh sand-silt mixtures containing 60% fines. For clean sand and specimens containing up to 30% fines, the results of this study on cyclic resistance were fairly consistent with previously published results.