Stability Analysis And Safety Evaluation Of Underground Pumping Station Cavern Of Long Distance Diversion Tunnel

Large-scale underground pumping station of long-distance water diversion project is located in the complex rock mass medium near the bank of the river,where the joint fissures develop and the groundwater exists.Due to the large scale of the pumping station,the fault area is generally distributed in the geological body around the project.The excavation of rock mass usually makes surrounding rock loose and causes stress redistribution,which led to large deformation and even partial collapse of the cavern.Based on the deep underground pumping station cavern of the Yellow River Diversion Project in Shanxi Province,the theoretical analysis,numerical calculation and in-situ monitoring are carried out to research the deformation and failure of surrounding rock during the excavation of large underground pumping station.And anchor cable support effect was studied.The results can provide important engineering practical significance and theoretical value for improving the safety and stability of underground cavern excavation and reducing engineering geological disasters.(1)Based on the theoretical study of rock mass and structural plane deformation,the mechanics and deformation properties of the surrounding rock and weak structural plane of large underground pumping station are analyzed.The influence of weak structures of different scales and grades on the damage degree of rock mass is discussed.The structural damage form and the calculation method of anchor support are systematically expounded and analyzed.(2)The finite element software ABAQUS6.14 was used to simulate and analyze the excavation and support process of underground pumping station.The spatial and temporal evolution of surrounding rock around the large underground pumping station building was given,and the prestress loss and long-term aging characteristics of anchor cable were analysed by simulate calculate.(3)Combined with the in-situ monitoring data,calculated surrounding rock displacement and anchor cable tension are verified,which proves the correctness of the calculation method and the rationality of the support measures.And the stability of the surrounding rock around the large underground pumping station cavern was evaluated.(4)The calculation and analysis method of the contact surface is studied by the finite element software ABAQUS6.14.The three-dimensional numerical calculation model reflecting the geometric parameters and mechanical characters of the structural plane is established.And the influence effect on the weak structural surface is analyzed.(5)Based on the numerical calculation results,the in-situ monitoring datas and the theoretical analysis,the excavation support parameters were optimized.The rationalization suggestions for the excavation procedures and supporting technical measures of large-scale underground caverns are put forward.