Analysis On Settlement Deformation Due To Different Underground Excavation Method Of New-built Metro Tunnel Under Existing Section Tunnel

With the growth of Chinese economy and population size of large and medium-sized city,the subway has become an important tool to ease urban traffic pressure,promote regional economic growth and benefit people's livelihood.The subway tunnel under the subway construction is inevitable,If the design and construction is not appropriate,the tunnel above the existing structure will produce greater deformation.And even affect the operation and structural safety of existing lines and even cause catastrophic accidentsThe deformation law of the ground surface and the existing structure of the tunnel in Beijing Metro is analyzed by means of data statistics,theoretical analysis,numerical simulation and field monitoring,the main work and achievements are as follows:(1)On the surface settlement caused by the excavation of single track tunnel,according to the rule of surface settlement,use three dimensional dynamic analysis,the superposition theory of surface settlement trough is put forward and the superposition formula of settlement trough is obtained,the theory is proved by the comparison between the model and the empirical data.(2)Based on the theory of settlement trough,the influence of the parameters of the surrounding rock,the depth of tunnel and the net distance on the settlement trough is studied and the relationship between the "W","U" type and "V" settlement trough and net spacing is obtained by numerical simulation.According to the standard of "U"settlement trough,the optimum distance standard of different surrounding rock condition and buried depth is put forward,and compared the size of the settlement trough caused by tunnel excavation under three different sections and analyzed their characteristics and advantages.(3)Analyzes the elastic unloading process of the existing railway in the next section based on the temperature Kerr elastic foundation beam model and the surrounding rock loose circle theory and the convergence constraint method.Analyzed the stress and strain of the sandwich soil and the existing railway line according to the historical process of tunnel excavation,According to the characteristics of three different tunnel sections,the application scope of the different surrounding rock condition and the interlayer soil thickness is divided.(4)According to the three types of tunnel and construction method,the numerical simulation is carried out under the existing tunnel,the deformation of the surface and the existing line of the three tunnels are compared(5)According to the deformation data of surface and existing monitoring,drawing the whole deformation curve and curve,analyzed the deformation law,and by comparison with the previous model data,expounds the relationship between the numerical calculation and experimental.