Liquefaction resistance of medium-dense Hostun sand under volumetric contraction

抄録

Liquefaction susceptibility assessments are heavily influenced by cyclic resistance curves derived through undrained element testing. The undrained experimental condition is based on the hypothesis that water flow and the resulting void redistribution is negligible within the time-frame of an earthquake. However, this hypothesis has come into question following recent analytical and experimental evidence. Depending on soil properties and stratification, localised, co-seismic volumetric strains can either facilitate or hinder the triggering of liquefaction. This paper is concerned with cases where partial drainage results in localised volumetric contraction. This condition could take hold close to the interface of a liquefiable layer with an underlying layer of lower permeability, or close to the interface of a liquefiable layer with an overlying layer of higher permeability. The aim of this work is to examine the effect of volumetric contraction on cyclic resistance. For the sake of simplicity, only constant rates of volumetric contraction are examined. The results presented are obtained using load-controlled cyclic triaxial element tests, performed on specimens of medium-dense Hostun sand. The undrained cyclic resistance curve is initially established. Subsequently, cyclic triaxial tests under constant volumetric contraction rates are presented. They reveal that volumetric strains can be of paramount importance, as even very small rates of volumetric contraction can have a dramatic effect on the number of loading cycles required to reach liquefaction.