Granular soils: from DEM simulation to constitutive modeling

Abstract

In this study, the distinct element method (DEM) was employed to numerically explore the mechanical responses of granular soils and to extract key components for an elastoplastic constitutive model for them. Considering the irregular shapes of real particles, a contact model considering rolling and twisting resistances was used in the DEM simulations. It is shown that this contact model can successfully capture the density-dependent, pressure-dependent behavior of granular soils as well as stress–dilatancy behavior. A critical state-based, double yielding surface constitutive model was used to describe the mechanical behavior of the DEM numerical material. A marked feature of the proposed constitutive model is the incorporation of a flow rule that defines the relationship between the stress Lode angle and strain Lode angle in the deviatoric plane. The model parameters were completely determined from DEM simulation results. The agreement between the DEM simulation results and the constitutive model prediction indicates that realistic complex mechanical behavior of granular soils in generalized loading paths can be reproduced well in both discrete and continuum ways. This will allow effective coupling of discrete–continuum modeling (such as DEM–FEM) in solving geotechnical boundary value problems with large deformation, where a consistent representative of soil is required for the near-field DEM modeling and far-field FEM modeling.