Abstract: As a kind of meshless method, the material point method (MPM) combines the best features of the meshed method and meshless method in the calculation, and avoids the mesh distortion phenomenon of the meshed method in solving large deformation problems. In the last decades, MPM has been successfully applied in a number of large deformation geotechnical problems and multiphase flow problems. Based on the theory and algorithm of the standard material point method, two multiphase MPM formulations were studied: the two-phase single-point formulation for saturated soil, and the two-phase single-point formulation with suction for unsaturated soil. To examine the accuracy and applicability of the multiphase MPM when simulating coupled hydro-mechanical multiphase flow problems, Terzaghi’s one-dimensional consolidation problem, one-dimensional compression wave propagation problem and one-dimensional seepage problem were simulated and the results were compared to the analytical solution. The simulation results show that the numerical solution is generally consistent with the theoretical solution, and the multiphase MPM can accurately describe the hydraulic characteristics of saturated porous media and the seepage characteristics of unsaturated porous media. Finally, the multiphase MPM was used to simulate the problem of rainfall infiltration in unsaturated slope, and the change of matrix suction and the whole process of large deformation failure of the slope under rainfall infiltration were analyzed.

Key words: multiphase material point method, two-phase single-point formulation, hydro-mechanical coupling problem