A fully coupled micro-hydromechanical (micro-HM) model for partially saturated soils based on DEM

A fully coupled micro-hydromechanical (micro-HM) model is developed for partially saturated soils in this study by integrating two-dimensional pore morphology (PM) approach and discrete element method (DEM). In the proposed model, the PM approach is employed to predict the tentative water distribution. The porous media marching cubes (PMMC) algorithm is adopted to evaluate the interphase interfaces and to further calculate the capillary forces. The combined effects of interparticle contact forces and the capillary forces on the motion of particles are handled by DEM. The developed model was then employed to conduct a series of numerical biaxial shear tests on a partially saturated soil with real particle shapes. The typical macroscopic responses such as stress–strain relationship, volume change, and saturation change can be well simulated by the micro-HM model. Based on the micro-HM model, a novel equation is proposed to directly evaluate the effective stress from the pore water distribution. The effective stress parameter and the suction contribution to effective stress calculated by the new equation well matches the experimental data, thus confirming the validity of the micro-HM model and the new equation of effective stress. The microscopic responses are then revealed and discussed through the proposed model.