Weakening laws of rock mass properties in blasting excavation damage zone of high rock slopes

The weakening of rock mass properties caused by blasting excavation has an adverse effect on slope stability. The Hoek-Brown (H-B) criterion is one of the effective approaches to quickly estimate the mechanical properties of the damaged rock mass. For blasting excavation of the left-bank arch spandrel groove slope of Baihetan Hydropower Station at an elevation of 834~750 m, the disturbance factor in the H-B criterion and its variation with the increasing depth are quantified by analyzing the acoustic wave velocities of the damaged rock mass after blasting. Based on this, the weakening laws of the rock mass properties in the damaged zone are studied. The results show that the disturbance factor decreases linearly as the depth into the slope face increases. In this case, the deformation modulus of rock mass increases linearly with an increase in depth. However, the increases are nonlinear in the uniaxial compressive strength, uniaxial tensile strength, internal friction angle and cohesion. Under blasting excavation disturbance, the uniaxial compressive strength is the most seriously weakened, while the internal friction angle is the lightest weakened. The research results can provide reference for the selection of appropriate rock mass parameters with regard to slope stability analysis and support design.