Study On The Influence Of Undercrossed Subway Shield Tunnel On The Existing Tunnel

With the constant expansion of subway construction, we will have to face the emergenceof a variety of new tunnels constructed beneath the existing tunnels, especially in the projectsof subway stations and transit tunnels. Therefore, it has become a key topic that needs to besolved in the undercrossed tunnel construction, involving the optimization of the design andconstruction of undercrossed projects, the supplementation and improvement of the existingstandards, and ensurance of operation safety of the exsting tunnel.Based on the theoretical analysis and the actual project of a subway shield tunnelundercrossing the existing tunnel, this thesis aims to study the deformation law of thesurrounding rocks in the project of new tunnel undercrossing the existing tunnel, with thenumerical simulation of Finite Element Software and the monitoring data of the project. Itproves that the shielding method used in undercrossing the existing tunnel is reliable, andgrouting reinforcement can effectively control the subsidence of surrounding rocks. Besides,it draws a conclusion that the construction can cause synergistic effect on the deformation ofthe surrounding soil body. The influence of the new shield tunnel undercrossing the existingtunnel mainly centers on the orthogonal point.According to the actual conditions of the project case, the thesis mainly studies andsimulates the law of mutual influence between the new tunnel and the existing tunnel. It alsooptimizes the construction parameters: the reasonable range of grouting radius of the newtunnel is2m～3m; the reasonable gabarit range is6m～12m which is1D-1.5D; thereasonable staggered distance ranges20m～35m. When the tunnel face of the new tunneldistances the existing tunnel less than10m and is out of reach of the existing tunnel, theconstruction footage each day is suggested to be less than2m; When the tunnel face of thenew tunnel is within the scope of the existing tunnel, the construction footage of the newtunnel should be less than1.5m. Based on the actual construction conditions, simulation, optimization of parameters, fieldtest data and related engineering experience, this thesis offers a number of key constructionmeasures in the undercrossed tunnel projects.