Fracture Behavior of Sandstone Under Multi-Loading Conditions Using DEM Framework

Abstract Failure of rocks under complex loading and progression of damage is of great interest to various rock engineering problems. In this context, the Discrete Element Method (DEM) has proven particularly effective in capturing fracture processes in rocks. However, DEM model parameter calibrations in most studies remain scenario-specific, restricting their applicability under varying loading conditions. To address this limitation, this study develops a DEM framework for sandstone under multiple loading conditions, employing a bilinear elasto-softening contact constitutive model that incorporates tension, shear, mixed tension–shear, and compression damage variables to rigorously capture its cohesive–frictional fracture behavior. A single, scale-independent set of DEM model parameters is derived for uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and Mode I fracture toughness (SCB) simulations by validating macroscopic DEM predictions against in-house UCS and BTS experiments. The results indicate that the DEM framework accurately reproduces stress–strain responses, peak and post-peak behavior, and fracture evolution, including macro-crack initiation and propagation. Detailed insights into progressive deformation and fracture in sandstone (UCS, BTS, and SCB simulations) are obtained through damage progression indicators (tension and shear) and stress–damage contour plots. Furthermore, a parametric analysis of DEM model parameters is conducted, and the critical parameters governing each simulation are identified.