Instability mechanism of dangerous rock masses on bank slopes containing a single shear band under the deterioration of reservoir water

Taking the Banbiyan dangerous rock mass as the focus, this study employs field investigations, model experiments, and numerical simulations to explore the instability mechanisms of dangerous rock masses on bank slopes containing a single shear band under the deterioration of reservoir water. The results indicate that the failure mode of the dangerous rock mass is collapse of rock mass in the hydro-fluctuation belt (HFB) – internal damage to the dangerous rock mass – development and through-going of fractures on both sides – sliding failure of the lower rock detaching from the parent rock. As the shear band gradually deteriorates, stress concentration develops around it near the highest water level. Within the rock mass close to the highest water level, a phenomenon of unloading occurs, and the pore water pressure at the shear band–bedrock interface eventually exceeds that within the rock mass of the HFB. In the numerical simulation, before 40 dry-wet cycles, the damage zone is concentrated near the shear band above the highest water level. Afterward, it concentrates around the fractures on both sides of the dangerous rock mass. The sensitivity of different shear band characteristics to the stability of the dangerous rock mass is ranked as follows: the height-length ratio of the shear band–bedrock interface, followed by the filling material thickness, dip angle, width, and degree of fragmentation. The findings can provide valuable reference for the stability and prevention of such dangerous rock masses.