Modeling of flexible coupling boundary combing discrete element method with finite difference method for drained/undrained triaxial test

Abstract

A simulation framework combining the coupling fluid method (CFM) and flexible coupling boundary method was developed to simulate drained and undrained triaxial tests. The discrete element method (DEM) model was calibrated using consolidated drained (CD) triaxial tests on saturated silt and then used to calculate the drained response of specimens with different initial porosity in both rigid and flexible boundaries. Subsequently, consolidated undrained (CU) triaxial tests were simulated and compared to the constant volume method. The bulk modulus of water was determined, and the reliability of the CFM was verified. On this basis, the DEM model was used to calculate the undrained response of the specimens with different initial porosity by simulating CU triaxial tests. The computed drained/undrained responses, including stress path, deviatoric stress, and shear-induced volumetric strain/pore water pressure, were consistent with the known behavior of silt. This study has promising potential to further enhance the understanding of granular behavior.