Simulation of triaxial compression tests with polyhedral discrete elements

The triaxial compression test is by far the most common laboratory test used to measure the mechanical properties of granular soils. In this paper, a series of simulations using the discrete element method (DEM) with polyhedral particles are introduced to simulate drained and undrained triaxial compression tests. A series of DEM simulations are first presented to replicate nine isotropically consolidated drained triaxial compression (CIDC) tests on sand specimens. The DEM micro-mechanical parameters of the inter-particle friction angle, normal and shear contact stiffness were calibrated using a single test in the series. The calibrated DEM model was then used to compute the response of other eight tests. The model gave very good estimate of the behavior for the other eight tests corresponding to a range of initial void ratios and confining pressures. The deviatoric stress and volumetric strains obtained in each CIDC test simulation show good agreement with the corresponding experimental data. The major source of error in the simulations is the use of larger particle sizes necessary to keep the computational cost manageable. The DEM model was then used to compute undrained response of the sand specimens by simulating isotropically consolidated undrained triaxial compression (CIUC) tests. The computed responses, presented in terms of the stress path, deviatoric stress, and shear induced pore water pressure, are consistent with our understanding of sand behavior. The simulations demonstrate that polyhedral DEM provides a suitable tool for representing granular material responses in triaxial shear without the need for use of complex input model parameters.