Shear Slip Instability Behavior of Rock Fractures under Prepeak Tiered Cyclic Shear Loading

In this paper, shear displacement properties of rock fractures were studied, and the energy evolution process was analyzed before sliding instability under complex shear loading paths. The artificial prefabrication method was used to simulate the natural rock fractures, which are difficult to obtain in the natural environment. The prepeak tiered cyclic loading tests under constant normal loading were performed on six rock specimens with fractures by rock direct shear apparatus (RDS-200). To obtain the stress difference of adjacent cycles, the direct shear test was conducted on the other six rock specimens with fractures before the prepeak tiered cyclic shear loading test. The variation trend of residual shear displacement (RSD) and the similarity of loading and unloading curves before slip instability were obtained by analyses of prepeak tiered cyclic shear loading test data. Energy evolution laws of rock fractures were analyzed with the consideration of the hysteresis characteristics, according to the hysteresis effect of shear displacement behind shear stress. This paper provides guidance for the study on shear instability of rock fractures under complex loading paths.