The Excavation Stability And Treatment Measure Of The Spillway Tunnel Slope In Jinping-â…  Hydropower Project

The paper focuses on the exit slope of spillway tunnel in Jinping-I Hydropower Project, taking 3-d numerical simulation to analysis the excavation stability. The appropriate treatment measure is proposed and each step of the construction is simulated and analyzed. The main points are:(1) In order to give reference to other people, and also support the follow-up calculation, the geologic information, pictures, literatures and reports are collected, and the engineering geology of exit slope of the spillway tunnel are fully depicted.(2) The merit and demerit of methods to obtain the rock and soil parameters are summarized, the limitation when applied on gravelly soil and the 3-d effect of slope are analyzed. Based on point safety factor method, the shear strength parameters of overburden gravelly soil are obtained by the parameter inversion.(3) Because of the huge scale of the model, in order to save time, based on the FLAC3D, dichotomy and fundamental principle of strength reduction method, the method of strength reduction is programmed, so can the safety of slope before and after excavation be calculated. Considering the force, deformation and velocity, the stability of the slope after excavation is analyzed, on the basis of which the slope retaining can be designed.(4) The common measures in slope retaining are compared with each other, the cutting-soil-to-reducing-weight and prestress anchor are finally selected to strengthen the overburden slope. The merits of prestress anchor are summarized, as well as its applicability in this project. Considering the safety of the slope, the frame beam is replaced by reinforced concrete stick slope wall.(5) The numerical simulation of prestress anchor stick slope wall is introduced and work progress of excavation and retaining of the overburden slope is analyzed. The results show:because of retaining structure, the main slide direction is changed with excavation, the strengthen measures adopted confines the deformation after excavation effectively, and turns the huge scale deep layer slide into small scale shallow slide, so can we say the measures adopted in the slope are effective. The safety factor is calculated by the programmed strength reduction method, supporting the construction of the project strongly and reasonably.