Static And Dynamic Analysis Of The Outlet High Slope Of The Tailrace Tunnel Of Pubugou Hydropower Station

Pubugou hydropower station is a state key project and a symbol of western development, located in Hanyuan and Ganluo County, Sichuan Province, has 3300MW installed capacity, 926MW firm output and 51.77 billion m3 total storage capacity , the project is built for electricity generation, flood control, sand barrage, etc. The maximal height of the vertical core-walled rockfill dam is 186m.Pubugou tailrace tunnel, adopted "three machines one tunnel" and free level tunnel schemes. The high slope of the outlet and open channel nearly 200m high and 400m long, takes to eastwest. The stability problem is relatively prominent for strongly unloading of granite rock, flourishing of small faults, diabase and joints; In order not to affect the built left upper road and the slope, the outlet slope should be greatly steeper than the suggested plan, and strong engineering measures should be applied. And then the stability of the slope and the safety of the lower outlet structure can be guarantied.According to these situations systematical research work is conducted: 1. Based on the topographic and geologic feature of the outlet section, 3-D model is established, unfavorable geologic structures such as the faults, joint fissures and cracks are fully considered. 2. Excavating steps of the slope and the tailrace tunnel are simulated. 3-D finite element method is applied to study unloading feature of the natural slope and excavating one. And the failure parts, which are the foundation of the reinforcement measure, are opened out. 3. According to the failure parts of the slope, the effect of reinforcement measures such as system anchors and prestressed steel cables are studied, and these schemes are compared to conclude the final optimal one. 4. The slope dynamic feature in function of earthquake is studied, and the deformation, velocity, acceleration and stress features of the slope are revealed. 5. The areas of the five yielding circles in different fit conditions of Drucker-Prager and Morh-Coulomb yielding rule are ordered. Failure areas of Pubugou natural slope computed by the five yielding rules fit in with relation of the five yielding sufaces when the value of approaches ,which is the ratio of internal angle length to external angle length of C-M hexagon.