Longtan Hydropower Station Underground Powerhouse Caverns Of Surrounding Rock Stability Study

The scale of the underground power house of Longtan Hydropower Station is one of the biggest in the world at present. Its power generation system includes 119 caverns whose total length is 30km. The caverns are stationed on the left bank of the dam in less than 0.5km~2 mountain body, and they are overlaped with each other and numerous crossing. So it is a veritable underground caverns systerm.The underground power house of Longtan Hydropower Station is mainly composed of main workshop, bus holes and main transformer room. It is belonged to the long-span, high-sidewall,. and close quarters underground caverns. So the research on the stability of the underground caverns is very important to the support structure design and the safety during operation.This paper makes lots of research on the rock mechanics property of the underground caverns in Longtan hydropower station. On this basis, the overall three-dimensional elastic-plastic finite element model of the underground caverns is established by ADINA (a finite element program for automatic dynamic incremental nonlinear analysis). This paper also makes many researchs on the surrounding rock's stress state and deformation character of the main cavern and key parts, and analyses the sensitivity parameter of the surrounding rock.The analysis shows that compared with the excavation in the aclinic and layered rock caverns, the surrounding rock's deformation of the caverns of Longtan Hydropower Station which locate in the steep and layered rock has obviously non-symmetric and distinct displacement along layers during the process of excavation. The overall deformation of the main workshop is the maximal, the stability of the caberns is fairish. From the result of the sensitivity analysis, we can see that the change of the parameter can affect the displacement of surrounding rock greatly, even though the change of the same parameter will affect different parts diversely.