An endochronic approach in modeling liquefaction of sand

Liquefaction is the transformation of cohesionless saturated soil skeleton from loose to dense state causing reduction of shearing resistance due to increase in pore water pressure and drop in effective stress. Understanding the liquefaction behaviour is limited mainly to empirical approaches, although progress has been made in constitutive modeling, models which could account for the volumetric changes due to variations in effective stress and that could realistically capture the liquefaction phenomenon were seldom achieved. In the present study a pseudo coupled endochronic viscoplastic constitutive model is developed to study the liquefaction behaviour of sands. Endochronic model is based on the observation of the state of stress in the neighborhood of a point in a plastic material and rapidity of deformation of the neighborhood. The model incorporated in to FLAC 3D using user defined constitutive model is validated with static and cyclic triaxial test data and is found to predict accurately the liquefaction phenomenon.