Stress based multi-contact model for discrete-element simulations

The aim of this study is to introduce a stress-based non-binary contact model missing in classical discrete element method (DEM). To tackle this issue, a classical force-displacement contact law is generalized by utilizing the trace of the particle stress tensor to make all contacts dependent on all other contacts of a particle and thus, to account for multiple contacts simultaneously acting on a single particle. Simulation results for uniaxial confined (oedometric) compression employing our new multi-contact model were compared with the classical discrete element formulation, an existing strain-based multi-contact model, and experimental data. The satisfactory agreement between these results supports the validity of our new contact model. Several test examples at higher load levels show that our generalized contact model is able to capture the stronger non-linearity at higher stresses. Due to its simplicity, the proposed multi-contact model can easily be integrated in any DEM implementation, remaining relatively fast when compared to more complex methods or even a discretization of particles, e.g. by FEM. Graphical Abstract: [Figure not available: see fulltext.].