Study On The Stability Oflarge-section And Small-spacing Metrostation Of Steep Joint Rock Stratum

With the acceleration of China's urbanization process,the original urban road has been unable to meet the travel requirements of growing population,as a new travel tool,rail transportation in large and medium-sized cities has brought a lot of convenience for people living in cities.The track in Chongqing is constructed by undermining because it is in rock stratum,in the construction process,the surrounding environment is often irreversibly affected,such as building cracks,surface subsidence,groundwater hydraulic changes,etc.In the actual construction of underground engineering,the rock mass is affected by joint surface,ground water,excavation method and supporting structure,which has poor surrounding rock stability,high risk and difficult in construction of the station.In this paper,the finite element numerical simulation method is used to simulate and analyze the construction process of the Tu Shan Station of Chongqing Rail Rings.The main results are as follows:?Firstly the classification of the buried depth of the tunnel is summarized,on this basis,Tu Shan station is divided into a shallow buried tunnel;secondly,the division of tunnel section and spacing is summarized,according to this,the station tunnel is classified into tunnel with large section and small clear distance.?According to the factual situation of site in Tu Shan station and the relevant design data,three construction methods of CRD,CD and double side-wall heading excavation are simulated,through comparison and analysis for simulation results,double side-wall heading excavation method is selected as the optimal excavation scheme for Tu Shan station finally.?The numerical simulation is carried out under the condition of joint stratum and homogeneous surrounding rock without joint by assumption in Tu Shan Station,by analyzing the displacement characteristics of tunnel surrounding rock and the stress characteristics of supporting structure,the intersection of the tunnel and the joint should be paid attention to in actual construction are summarized.?Since the station is in the joint stratum,there is a bias effect,double side-wall heading excavation method of the four different excavation sequences and different supporting parameters are used for optimization analysis,finally,the excavation sequences with relatively more excavation faces and relatively small displacement,the optimum bolt length of most 6m and local 4.5m,and the optimum combination of shotcrete 0.33 m and steel frame spacing 0.5m are selected.?Through the three-dimensional numerical simulation analysis of Tu Shanstation,it is found that the vault subsidence value and horizontal convergence value of the right hole are obviously larger than that of the left hole;the maximum value of surface subsidence occurs at the surface above the vault of the right hole;local tensile stress occurs in the main vault and the bottom area;the surrounding rock of the arch foot of the left hole is more likely to shear failure;the molding zone occurs at the sidewalls of the right hole and runs through the whole contact passage.?The reliability of the finite element simulation is verified by comparing and analyzing the actual monitored data with the numerical simulation results.The tunnel is stable and safe in the construction process.