Three-Dimensional Numerical Modeling of Grain-Scale Mechanical Behavior of Sandstone Containing an Inclined Rough Joint

We intercompare highly constrained physical experiments with a three-dimensional bonded-particle discrete element model. The models incorporate a single inclined rough joint at various inclinations to simulate the mechanical response of fractured-rock from micro-scale cracking through crack-coalescence and culminating in macro-scale rupture. This approach combines the scanned 3D surface morphology of the real joints with a smooth-joint contact DEM model to overcome the problem of using a simplified geometry that cannot truly reflect the effects of joints on rock mass response. In both the physical samples and in the modeling, the inclination angle of the joint was varied between 0° and 50°, and the samples were tested under confining stresses in the range 0–40 MPa. The numerical test results indicate that: (1) confining stress has a significant strengthening effect on the jointed sandstone; (2) a threshold angle of ~ 40° of the inclined joint controls failure; (3) when the inclination angle is less than ~ 40°, failure is through the intact rock with some tensile fracturing around the joint and when greater than ~ 40° slip occurs on the joint with shear fracturing concentrated near the joint surface; (4) the 3D numerical approach replicates the deformation history and evolving texture of the jointed sample response with high fidelity, including the evolution of micro-scale features of progressive failure. The three-dimensional bonded-particle discrete element modeling represents a systematic verification of, and extension to, laboratory tests, presenting a viable model to emulate the mechanical behavior of jointed rocks with the potential to enhance the predictive capability of modeling while still maintaining reasonable computational efficiency.