Study On The Stability Of Tunnel Surrounding Rocks In High Geo-Stress Zone

With the exploitation of hydropower of western region in China, many large scale hydropower projects come forth. High mountains, deep valleys, and steep topography are the characteristics of Western region, so it is an effective way of hydropower exploitation to develop long tunnel diversion hydropower. The high geo-stress in western region, however, is the strongest in the world, which brings new challenges and problems to the construction of hydropower projects in large scale under this complex geology condition.In this study, with the diversion tunnel in Jinping Cascade II Hydropower Station as the research object, FLAC, a numerical analysis method, was used to analyze the stress distributions and deformations of high geo-stress zone after excavation of caverns, through the numerical simulation of the dynamic change process of surrounding rocks. Further, on the basis of the further discussions of the influences of residual strength on the calculation results and the analysis of anchor stress, the reasonable time of installing anchor structure was put forward.Based on 2-D numerical model, the sensitivity of the parameters of surrounding rocks was analyzed. Moreover, the one-parameter variation analysis method was adopted not only to identify the sensitivity of the influences of parameters on the mechanical effect of surrounding rocks, but to differentiate the primary parameters and secondary parameter which provides the base for the selection of parameters and analysis of calculation results, as well as the effects of construction sequence of alternately digging among caverns were studied that may supply reference for design and construction.