Abstract:Based on the theories of structural damage and multi-surface model,a new elastoplastic model for saturated clay subjected to cyclic loading is deduced by combining the mixed strain hardening with the isotropic shear and compression damage. The structural damage of clay is depicted by the shear and compression damage variables,and the damage evolution equations are presented on the basis of accumulated plastic deviatoric strain. It is shown that considering the shear and compression damages can describe the changing process of Poisson's ratio under undrained condition. The model is verified by simulating the seismic response of saturated clay subsoil. Results show that considering the modulus damage may cause the difference between the plastic moduli of the loading and unloading,making the latter greater than the former. Further,this difference makes the plastic strain response during the loading greater than that during the unloading and as a result,the plastic deviatoric deformation accumulates with the continuation of cyclic loading.