Multiscale, multiphysics modeling of saturated granular materials in large deformation

We propose a multiscale, multiphysics approach by coupling two-phase material point method (MPM) with discrete element method (DEM) (MPM-DEM) to simulate the hydro-mechanical coupling responses of saturated granular media from small strain en route to large deformation under either quasi-static or dynamic loading conditions. The multiscale scheme is featured by (a) using a two-phase MPM in conjunction with the u−v−p formulation to solve the solid–fluid interactions in the macroscopic domain of a boundary value problem of saturated porous media, and (b) employing a DEM assembly comprised of arbitrarily shaped particles to provide path-dependent effective constitutive responses for each material point under complex loading conditions. A semi-implicit integration scheme based on the fractional step algorithm is further implemented in the proposed multiscale approach to improve its overall efficiency. The proposed approach is validated by the one-dimensional consolidation test before being further used to simulate more challenging problems, including the cyclic shaking test, the column collapse, and the wave propagation in anisotropic saturated porous media. We demonstrate that the proposed MPM-DEM approach is powerful and versatile in capturing the complicated static and dynamic multiphysics interactions exhibited in saturated granular media that could be of practical importance in various engineering settings. We further establish connections between these macroscopic observations with their underlying microstructural mechanisms to offer multiscale insights into the complicated dynamic responses of saturated sand.