Static Liquefaction Response of Medium Dense Silty-Sand of Chang Dam

Instability and static liquefaction of medium dense silty-sand, which has experienced liquefaction during the devastating 2001 Bhuj, India, earthquake has been explored in the current research. Unlike previous studies, where static liquefaction has been reported to be prevalent in very loose sand as well as in loose silty-sand specimens, the findings in the present article reveal its occurrence in medium-dense silty-sand. Interestingly, the soil exhibited static liquefaction even at large confining pressures amounting to 200 kPa and 300 kPa (besides 100 kPa) indicating its susceptibility to complete loss of strength at greater depths. Experimentally observed mechanical behavior has been compared with the response predicted by using a non-Associative state dependent elasto-plastic material model that can capture strain softening behavior in granular media. Vanishing of second order work indicated the onset of instability and evolution of hardening modulus captured subsequent liquefaction in the experimental results as well as model predictions. Specimens exhibited runaway instability when undrained boundary condition was imposed at stress states lying in the region of potential instability. Microstructural instability (liquefaction) within the soil mass has also been examined using disturbed state concept (DSC).