Weakening mechanism of shear strength of jointed rock mass considering the filling characteristics

The shear strength of a jointed rock mass is a key factor for evaluating the overall stability of an engineering rock mass. Fillers have an obvious weakening effect on the shear strength of a jointed rock mass In this paper, experiments are conducted to study the mechanism by which the shear strength of a jointed rock mass filled with gypsum is weakened under hydraulic coupling effects. The experimental results are as follows. (1) During the shear process, a multipeak phenomenon can be observed in the shear displacement–shear load curve, and the existence of backfill delays the occurrence of peak shear stress. (2) The thickness of the filler obviously weakens the peak shear resistance of the rock mass by up to 53.65%. The reduction rate of the peak shear stress is positively correlated with the normal stress. In terms of the shear strength, the greater the thickness of the filler is, the greater the cohesion and the smaller the internal friction angle of the jointed rock mass. (3) The sensitivity of the peak shear stress of the filled jointed rock mass to the water content of the filler is lower than that to the thickness of the filler. The maximum reduction rate of the peak shear stress of the rock mass caused by the water content of the filler is 54.55%. Within a certain range, the greater the water content of the filler is, the greater the cohesion of the jointed rock mass and the smaller the internal friction angle.