Research On The Influence Of Shield Construction Of Small Radius Tunnel On Adjacent Railway Bridges

With the improvement of the urban rail transit network,a single linear tunnel can no longer meet the demand.The new tunnel is inevitably close to the building structures,which is bound to endanger the building structures and even cause serious safety problems.Therefore,this paper relies on a tunnel in Zhengzhou area to cross the intercity railway bridges.According to the relevant specifications,in order to ensure the operation safety of the railway lines,the shield tunnel crossing the railway bridges construction needs to set up isolation pile protection measures.Midas GTS NX finite element software is used to simulate the construction of small radius shield tunnel crossing railway bridges with and without isolation piles.The effect of isolation pile protection measures during the construction of small radius shield tunnel is studied,and the accuracy of numerical calculation is verified by monitoring data.This has important engineering practical value for the construction of shield tunnel crossing railway bridges safely.The main research results are as follows:(1)According to the numerical calculation results under the condition of no protective measures of isolation piles,it can be seen that the maximum differential settlement deformation of adjacent piers is about 3.3 mm,which is likely to endanger the operation safety of railway lines during the constructions.(2)According to the numerical calculation results under the condition of protective measures with isolation piles,it can be seen that the isolation piles can effectively reduce the differential settlement deformation of adjacent piers and abutments,the horizontal and vertical deformation of bridge piles during the construction of small radius shield tunnels.Compared with the protective measures without isolation piles,it is more conducive to the operation safety of railway lines during the constructions.(3)According to the numerical calculation results,it can be seen that the greater the net distance between the bridge piles and the tunnels,the weaker the adverse effect of shield tunnel construction on the bridge structures;the influence range of shield tunnel construction on bridge piles is about 3D(D is the tunnel diameter)before and after the bridge piles along the shield tunneling direction.The surface settlement deformation curve caused by shield tunnel crossing the railway bridge constructions is approximately ’W’ type distribution.(4)Compared with the monitoring data,the accuracy of the numerical calculation results is verified,and it also shows that the isolation pile protection measures can better ensure the operation safety of the railway lines during the construction period,which proves the effectiveness of the isolation pile protection measures.In this paper,the influence of construction on the surface and surrounding environment is analyzed by using the research method of numerical simulation and monitoring data,and the deformation law of railway bridges with or without isolation pile protection measures is analyzed.In order to ensure the operation safety of railway lines during construction,it is necessary to set up isolation pile protection measures.The research content of this paper can provide some guidance for subsequent similar projects.