Correlation of shear wave velocity with liquefaction resistance for silty sand based on laboratory study

Several methods have been used for the evaluation of liquefaction potential, among which the simplified method is mostly used. In this method, which is mainly based on standard penetration test (SPT), cone penetration test (CPT) and shear wave velocity (Vs) measurement, a boundary curve is provided to separate the liquefiable and non-liquefiable soil zones. Vs measurement is a good alternative method of penetration-based methods (SPT and CPT). This is especially true in micro-zonation of liquefaction potential. Although relatively large studies have been carried out to establish the correlation between Vs and liquefaction resistance for sands; there are uncertainties about the effects of non-plastic fines on the correlation. The objective of this research is to study the effects of fines on the correlation of Vs and liquefaction resistance. In this regard, the cyclic triaxial and bender elements tests have been performed, and Vs and liquefaction resistance of a clean sand and four combinations of this sand with non-plastic fines up to 25% have been measured. A simple, semi-empirical, semi-analytical method is proposed to establish a correlation between Vs and liquefaction resistance. The effects of non-plastic fines on Vs and liquefaction resistance of silty sands have been examined in this study, and the effects of non-plastic fines on the correlations between these two parameters are considered. The results in this study show that an increase in the ratio of silt to sand will result in a decrease in Vs and liquefaction resistance. Based on these results, it is argued that the correlation between Vs and liquefaction resistance of various combinations of sand and non-plastic fines are soil specific. Also based on the results of this study, it is found that the existing methods of liquefaction potential evaluation which are based on Vs may underestimate or overestimate the liquefaction resistance of silty sands.