Stability Analysis of Diversion Tunnels in Hydropower Plant Subjected to Initial Impoundment

The initial impoundment of hydropower plant leads to the zooming water level of reservoir. The seepage filed of rock mass then forms and will be a potential threat to the structural stability of tunnels neighboring the reservoir. The strength reduction method and overloading method are proposed to respectively analyze the structural stability of rock and lining structures after the initial impoundment. By adopting the presented approaches, corresponding safety factor can be obtained and used to assess the safety margin. A case study is done. The proposed methods are respectively employed to analyze the surrounding rock and lining structures of the diversion tunnel at Jin´anqiao hydropower plant. The results show that the presented methods not only can simulate the damage evolution processes, but also calculate safety factor of surrounding rock and lining structures, which indicates that the proposed methods are effective and reliable.