Analysis Of Influence Of Train Dynamic Load On Settlement Of Metro Shield Tunnel

Based on the geological survey data and field settlement monitoring data of a certain section of Shanghai rail transit,this paper analyzes the vertical deformation law of ground around shield tunnel under the action of train dynamic load,and studies the settlement law of tunnel during operation period.According to the results of indoor geotechnical test,the physical and mechanical parameters of the soil layer are determined,and the mechanical characteristics of the subway shield tunnel during the operation period are fully considered.The theoretical analysis method and finite element analysis method are used to simulate the influence of train dynamic load on the ground settlement around the tunnel.Through the simulation of the settlement law of each node caused by single and multiple subway train dynamic loads,combined with empirical formula,the linear time history,short-term and long-term cumulative plastic deformation are calculated.In the analysis process,the two working conditions of single and double hole tunnel are compared and analyzed.Finally,the reliability of numerical simulation is verified by comparing the theoretical calculation results,finite element analysis simulation and actual monitoring data1.In the case of different train operation time,the maximum vertical displacement caused by single dynamic load decreases with the increase of speed,and the influence on double tunnel is slightly less than that of single tunnel2.Under the condition of constant train speed,the maximum vertical displacement of tunnel caused by single dynamic load increases with the distance from the loading point.At the same time,the fluctuation amplitude of the maximum vertical displacement decreases with the increase of the distance from the loading point.3.Under the condition of constant train speed,the vertical deformation trend of each node in the horizontal direction of the tunnel is similar to normal distribution.The main influence range of train dynamic load on the tunnel bottom surface is about 15 m on both sides of the dynamic load point.4.Under the condition of constant train speed,the displacement time history curve of dynamic load cyclic loading is similar to that of single loading,and the increment of accumulated settlement increases gently,and the increase decreases with the increase of times.5.Under the action of long-term dynamic load cyclic loading,the cumulative settlement of tunnel increases with the increase of operation years,however,the increase range decreases with the increase of operation years,and the slope of curve gradually flattens with the increase of operation years.The research results can provide certain reference for the deformation prevention and treatment of urban subway tunnel,and ensure the safety of subway operation.