Multi-scale modelling for granular materials using material point method and discrete element method

Abstract

Granular materials are composed by discrete particles, which are often observed in geo-hazards, such as debris flows. It is difficult to establish unified constitutive relations to describe the multiple-state properties of granular materials, i.e., solidand fluid-like states and in-between transitions. In this study, a hierarchical multi-scale modelling scheme is developed based on the concept of black box theme. The macroscopic behavior is modelled by using material point method (MPM), which is suitable for large deformation treatment, while the constitution relations at each material point are extracted from discrete element method (DEM) modelling. By using the MPM/DEM modelling, the collapse of a sand pile is simulated and compared with experiments. The correlations between macroscopic phenomenons and microscopic network of force chain are illustrated. This MPM/DEM multi-scale modelling does not need any constitutive relations, and facilitates effective cross-scale interpretation and understanding of granular flow behaviors. It provides a potential approach to study the multiple states and large deformations of granular materials, especially when the constitutive relations cannot be expressed explicitly.