Abstract:The stress equilibrium equation,the continuity equation for water and the elastoplastic matrix are established. By using the Galerkin method,all the governing equations are discretized in the space domain and time domain respectively;and a two-dimensional FEM code for coupled hydro-mechanical elastoplastic analysis of saturated-unsaturated porous medium is developed. By introducing one set of special computation equations related to the unsaturated state,a numerical computation is carried out for the assumed coupled hydro-mechanical problem in an unsaturated soil body. The displacements,the pore pressures,the effective principal stresses,the flow velocities and the plastic zones at different times in the soil body are investigated;and the validity of the code is tested and verified qualitatively.