Numerical characterization of sandstone's mechanical responses under multi-level compressive differential cyclic loading (DCL): A 3D particle-based numerical investigation

The mechanical response of rocks subjected to compressive differential cyclic loading (DCL) with various stress rates is rarely investigated via numerical simulation at the microscopic level. In this study, the behaviour of sandstone is numerically investigated via a 3D particle-based numerical model. A damage model is implemented based on the variation in bond diameter and succeeds in accurately reproducing the stress-strain relations obtained from laboratory tests. Three evolution patterns of bond diameter are used to duplicate the strain rates observed during the laboratory tests. A system similar to AE monitoring is run in simulations, and AE events are recorded, classified, and visualized according to the magnitude of released energy at bond failure. The effect of heterogeneous bond strengths on AE characteristics is discussed. A heterogeneous model is recommended for the realistic reproduction of the onset of cracking as well as stress dependency. A stress rate-induced phase shift in terms of the stress-strain relation is observed in both laboratory tests and numerical simulations. The damping effect is thoroughly considered in the numerical model.