Hysteresis Characteristics of Rocks Influenced by Rough Interfaces: A Discrete Element Method Study

Interfaces at multiple scales within rocks critically control the mechanical properties of rock masses. However, the mechanisms by which interface roughness characteristics affect non-plastic deformation remain incompletely understood. In this study, particle-flow simulations were used to conduct loading–unloading tests on rough interfaces. The results show that contact surfaces inclined relative to the overall interface provide additional resistance during unloading and recovery, thereby increasing both the magnitude and likelihood of interfacial hysteresis. This mechanism explains why hysteresis can occur under loading normal to the interface. Differences between the static and dynamic friction coefficients, together with dynamic changes in the normal vectors of the contact surfaces, further intensify the hysteretic response. When deformation of the surrounding material is considered, the “lateral compression–expansion effect” caused by asperity extrusion and interlocking under compression, as well as the slip-induced “dilatancy effect,” also contributes substantially to rough-interface hysteresis. In addition, initial stress on crack surfaces can enhance the degree of hysteresis. The grain-based rock model incorporating interface roughness and in situ stress effectively reproduces the non-plastic hysteretic behavior of rocks.