A practical effective stress-strain model of sand is presented in which only the soil parameters directly obtained from a common site investigation and a laboratory test, i.e., G-�, h-� curve and liquefaction curve, are used as input parameters.A key mechanism simulating liquefaction and cyclic mobility behavior is modeled based on the accumulated damage concept for pore pressure generation with a generalized hardening model for shear behavior. The proposed model can simulate reasonably well the stress strain behavior of hollow cylindrical specimens subjected to earthquake loading.