Study On The Influence Of Large Section Rectangular Tunnel Closely Overcrossing Metro Construction

At present,China’s urbanization process is accelerating,while the large-scale construction of urban subway tunnels,the construction of rectangular pipe jacking underground crossing channels has further promoted the improvement of urban quality.In the process of rectangular pipe jacking construction,it will have a certain impact on the surrounding soil and buildings.In particular,the construction of large-section rectangular pipe jacking adjacent to the existing subway tunnel will cause great disturbance to the surface and the existing subway tunnel,thus affecting the safe operation of the existing subway.Therefore,it is of great significance to study the influence of large-section rectangular pipe jacking tunnel on the construction of existing subway tunnel.Based on the engineering background of a large section rectangular pipe jacking construction in Zhengzhou City,this paper uses Midas GTS/NX to establish a threedimensional numerical model to analyze the influence of large section rectangular pipe jacking construction on the surface and existing tunnels with or without pipe curtain measures.On this basis,the influence of different construction parameters on the existing tunnel is explored.Finally,the actual monitoring data are compared with the corresponding simulation values to verify the accuracy of the simulation.The main research results of this paper are as follows:(1)Based on the hydrogeological conditions of the project,the current situation of the existing subway structure and the relevant industry technical specifications,the safety impact level of the project,the deformation control standards of the existing subway tunnel and the surface are determined,and the selection of the pipe jacking machine is determined.(2)According to the results of numerical analysis,it is concluded that after the completion of large section rectangular pipe jacking construction,the surface deformation curve is distributed in a ’groove’ shape along the central axis of pipe jacking,and the maximum settlement value appears above the central axis of pipe jacking.The deformation curves of the left and right lines of the existing tunnel are in the shape of inverted ’V’,and the maximum uplift occurs at the cross section of the existing tunnel and the pipe jacking.The excavation unloading of pipe jacking is the main reason for the deformation of surface and existing tunnel.(3)Through the numerical analysis results,it is concluded that the influence of large section rectangular pipe jacking on the deformation of the ground surface is smaller than that of the non-measure construction,but the deformation control effect of the existing tunnel under the construction is better.(4)Through numerical analysis,the influence of different grouting pressure,soil bin pressure,jack thrust and net spacing of pipe jacking on the vertical deformation of existing tunnel is obtained.(5)By comparing and analyzing the monitoring data and simulation values of the surface and existing tunnels,it is found that the monitoring data and the simulation data have the same change trend,which verifies the accuracy of the numerical simulation.It shows that the influence of large section rectangular pipe jacking construction on the surface and the existing subway tunnel is within the control range,which does not affect the normal operation of the existing subway.