Study On New Subway Station Excavation Effect Of Existing Tunnel With Seamless Docking

The research on construction safety control of foundation pit has important theoretical and engineering value.Taking Changsha Railway Line 3 Changsha Railway Station Station seamlessly docked with existing Line 2 as the background,and the combination of soil plastic deformation theory,on-site monitoring and numerical simulation is adopted to study the deformation of foundation pit retaining structure,ground settlement and station displacement during foundation pit excavation.The main work of this paper is as follows.(1)The MSD theory method is adopted to analyze the deformation mechanism of foundation pit under cantilever excavation and internal support excavation,and the MSD method under hard soil condition is proposed.According to the principle of energy conservation,the soil displacement and the horizontal displacement of the wall are calculated by the improved MSD method.Comparing the theoretical calculation results with the monitoring results,the accuracy of the improved MSD method is indicated.The three parameters of excavation depth,support spacing and wall length are studied in detail,and the deformation laws of retaining structure and surface settlement were studied.(2)The whole process of excavation of Changsha Railway Station is simulated by ABAQUS.The results of numerical simulation,theoretical calculation and field monitoring are compared.On this basis,the deformation law of the vertical and horizontal displacements of existing stations is analyzed.From three aspects: sequence,excavation depth and lateral dimension of the foundation pit,the excavation plan is optimized.(3)The numerical model is built to simulate the deformation of the foundation pit excavation around the building.From the three aspects of building location,building height and building superposition effect,the horizontal displacement of the retaining structure and the settlement of the ground behind the wall are analyzed when the building is adjacent to the foundation pit.The deformation law of the soil is explored and the corresponding reinforcement is proposed.