Different roughness effects on the characteristics of fault sliding behavior

Fault surface roughness, a critical parameter influencing fault slip behavior, significantly affects fault sliding characteristics through variations in its hierarchy. This study focuses on Jinping marble as the research subject and systematically conducts fault friction tests under the combined effects of varying normal stresses and fault plane roughness (ranging from micrometer to millimeter scale). The aim is to elucidate the influence mechanisms of the synergistic effects of roughness and normal stress on fault sliding behavior characteristics. The main findings are as follows: (1) Fault surfaces with low to moderate roughness are more susceptible to inducing periodic stick-slip oscillations, with the magnitude of shear stress drop positively correlated to normal stress. Low-roughness fault surfaces can counteract the shear strength enhancement caused by roughness variations, thereby dominating the shear strength weakening process. In contrast, high-roughness fault surfaces, due to the dynamic separation effect of asperities, are more likely to trigger single stress drop events. As normal stress increases, local asperities tend to undergo brittle failure, resulting in a sudden decrease in non-periodic stress. (2) The stick-slip behavior of Jinping marble faults can be categorized into four typical modes: regular stick-slip, sub-regular stick-slip, pseudo-chaotic stick-slip, and chaotic stick-slip. Notably, chaotic stick-slip and regular stick-slip exhibit significant differences in periodic characteristics and stress curve morphology. Chaotic stick-slip frequently occurs during the transition phase between stick-slip and stable sliding. (3) The geometric morphology of the fault surface profoundly influences both the mechanical response and the characteristics of the acoustic emission (AE) signals during sliding. The amplitude of local strain reduction diminishes from the shear loading end towards the opposite end. The failure mechanisms of asperities on the fault plane demonstrate hierarchical dependence: frictional wear dominates at low roughness, brittle fracture at high roughness, and a combination of both mechanisms at moderate roughness. Furthermore, the AE signal responses reveal the underlying energy release mechanisms during fault sliding. These research findings provide technical support for the safe development of deep-seated resources.