Multiscale modeling of large deformation in geomechanics: A coupled mpm-dem approach

Numerical modeling of geotechnical problems frequently requires the consideration of large deformation soil responses. The Material Point Method (MPM) has gained increasing popularity recently over many other methods such as Finite Element Method (FEM) in continuum modeling of large deformation problems in geomechanics. This study presents a new enrichment of MPM with multi-scale predictive capabilities. We propose a computational multiscale scheme based on coupled MPM and DEM following a similar concept of the FEM-DEM coupling scheme [2, 3]. The MPM is employed to treat a typical boundary value problem in geomechanics that may experience large deformations, and the DEM is used to derive the nonlinear material response required by MPM for each of its material points. The proposed coupling framework helps avoid phenomenological constitutive assumptions in typical MPM, while inherits its advantageous features in tackling large deformation problems over FEM (e.g., no need for re-meshing to avoid highly distorted mesh in FEM). Importantly, it provides direct micro- macro linking for us to understand complicated behavioral changes of granular media over all deformation levels, from initial elastic stage en route to large deformation regime before failure. Several demonstrative examples are shown to highlight the advantages of the new MPM-DEM framework, including the collapse of a soil column, biaxial shear tests and different failure modes observed in a footing problem in geotechnical problems.