3D DEM-based analysis of cylindrical rock specimen failure and micro-fracturing: impact of stiffness and tensile strength

Rock failure triggering with micro-fracturing poses significant challenges in engineering practices. In this study, the failure mechanism of the rock specimens was investigated focusing on the impact of stiffness and tensile strength on rock fracturing. To achieve this, uniaxial compression tests were simulated using the discrete element method for three rock types including granite, sandstone, and limestone. To enable elastic interactions at particle contacts for diverse rock material responses under stress, a linear parallel bond model was utilized. This model allows for elastic interactions while permitting slip, effectively simulating the complex behavior of rock materials under stress. The results revealed distinct mechanical behaviors among the three rock types, with granite exhibiting the highest peak stress and a steep stress–strain curve, indicative of its superior compressive strength. In contrast, sandstone shows lower peak stress and earlier failure due to its higher porosity and lower cohesion, while limestone demonstrates significant plastic deformation before failure, resulting in a more ductile response. Increased stiffness correlates with higher final strain values across all rock types, with limestone showing the greatest sensitivity to stiffness changes. The study demonstrates that increased tensile strength leads to higher peak stress and strain values, significantly delaying failure mechanisms, with a threefold increase in tensile strength resulting in a 1.47-fold increase in final stress for granite and a 2.46-fold increase for limestone. The analysis of crack development indicates that both stiffness and tensile strength substantially influence crack formation and distribution, particularly in sandstone.