ABSTRACT
A numerical model is presented for the partially saturated sandy soil in seismic area, with the particular interests on the liquefactions. The formulation is based on Coussy’s unsaturated poromechanical theory with reasonable assumptions for sandy soils. Based on the conception of effective stress, a constitutive equation with two loading surfaces is used for describing the mechanical behaviour of sandy soils under cyclic loading. And then it is applied to study the dynamic response of free filed under the earthquake loading. It is shown that, with the decrease of the initial water saturation, the liquefaction resistance increases. The variation of initial water saturation will also have the influence on the dynamic responds. And its frequency will also have some changes.
