Failure process and long-term stability analysis of typical unstable rock mass in the Three Gorges Reservoir area considering rock mass deterioration

Abstract

Since the Three Gorges Reservoir went into service, the rock mass in the hydro-fluctuation belt of the bank slope has obviously deteriorated, which accelerates the instability of the bank slope. The potential debris avalanche threatens the safety of the Yangtze River waterway. The Banbiyan unstable rock mass in the Three Gorges Reservoir area was studied using the shear strength reduction method to analyze the failure process and long-term stability of the unstable rock mass under rock deterioration. The results show that the Banbiyan unstable rock mass is stable under natural working conditions. Under reservoir water and rock mass deterioration, the tensile stress is concentrated at the central section. The tensile cracks gradually penetrate up and down, extending to the prominent controlling cracks at the top and the bottom base fracture zone. Slip-shear failure may occur. Under the condition of reservoir water combined with rock mass deterioration and heavy rainfall, the strength of the rock mass decreases by 30% after about 40 hydrological cycles, and the stability coefficient of the Banbiyan unstable rock mass decreased to about 1.14, which is an under-stable state. It is suggested to carry out engineering prevention and control to improve the stability of dangerous rock mass to ensure the safety of the waterway. The research results can provide a scientific and reasonable basis for disaster prevention and mitigation of the Banbiyan and similar unstable rock masses in the Three Gorges Reservoir area.

Keywords

• three gorges reservoir area
• banbiyan
• unstable rock mass
• rock mass deterioration
• long-term stability