Research On The Structure Deformation And Control Under The Conditions Of Shield Tunnel Undercrossing The Beijing Subway Double Shield Section

ABSTRACT:As the rail transit network continues to expand and ground buildings become more intensive. Some of the newly constructed metro lines will cross the municipal pipelines and existing lines inevitably,especially project of shield tunnel undercrossing the existing subway shield section in short vertical distance with great difficulty and high requirement.Therefore, it is necessary to carry out systematic research of the deformation law of the existing lines and the dynamic response of track structure in the project of shield tunnel undercrossing the existing subway shield interval,so as to optimize construction control measures in order to guarantee the safety of the existing subway operation.With the rapid development of rail transit,crossing projects are increasing,this research is instructive to the development of urban subway and underground engineering.Based on widely literature review,the project of a shield tunnel undercrossing the existing subway double shield section is taken as the research object,in the project,the vertical distance between shield tunnel and the existing subway section is6m(1.0D) and the exsiting subway is in the shield strongly affected zone.In addition the project has the characteristics of complicated variability of geological condition and project uncertainty.However,the settlement of the existing subway structure is only0.98mm in the process of shield crossing. This is the first typical engineering that the shield tunnel crosses the existing subway shield section successfully in the Beijing area.The main research contents are as follows:(1)Use finite element software ANSYS to establish three-dimensional stratum structure model,to analyze the influence on the existing subway section crossed by shield construction based on the theory of continuous medium.(2)Combined with the actual construction situation,through the analysis of monitoring data in the construction process and comparing with simulation results,to verify the accuracy of simulation,then to conclude the influence regularity on the existing subway caused by synchronous grouting and secondary grouting.(3)Based on the success of crossing project and combined with the numerical prediction and analysis of monitoring data,as while as the management process of the case,a preliminary study of risk management processes of shield tunnel crossing the exsiting subway shield section has been presented;The active and passive measures of shield undercrossing shield section are analysed and explored,then the risk control process of the shield crossing exsiting shield project is formed to ensure the smooth operation of the crossing engineering.(4)By using the ABAQUS finite element software, a vehicle-track-tunnel three-dimensional coupling dynamic analysis model is built based on the static analytical result. After analyzing effect which the track structure deformation may have on the vehicle running and track dynamic properties, a series of reasonable advice are given to guarantee the operation safety of the existing line.