Research On Deformation Law Of Multi-section Tunnel Group Passing Through Existing Subway Station

In recent years,the society and economy have developed rapidly.With the expansion of the city scale,the construction of urban rail transit is bound to get rapid development,so the development scope of underground area is wider,leading to the new underground engineering inevitably form a three-dimensional intersecting system with existing structures,interval tunnels,stations and so on.In particular,special projects such as multiple tunnels closely passing through existing subway stations have large influence scope,poor controllability,long construction period and large disturbance,so it is very difficult to guarantee such underpass projects.Therefore,This paper aims at the problem of how to successfully construct multiple tunnels under the subway station,taking an interval tunnel and the entrance and exit section tunnel in Beijing as the engineering background,this paper studies the settlement law of multi-line tunnel underpass an existing subway station by theoretical analysis and numerical simulation combined with field monitoring technology.The main research results are as follows:(1)Based on the two-stage analysis method of random medium theory and elastic foundation beam theory,the subsidence deformation caused by the excavation of multiple tunnels is studied firstly,and the deformation of the existing station structure caused by the construction of multiple tunnels under close alignment is analyzed secondly.(2)In this study,the influence of the construction sequence of each guide tunnel between the flat top straight wall section tunnel and the horseshoe section tunnel of the two entry and exit sections on the settlement and deformation law of the existing subway station is calculated and analyzed by using three-dimensional finite element numerical simulation software based on actual engineering cases.Through process control analysis,the influence degree of each key construction process and construction stage on the settlement deformation of the existing subway station is studied,and the mechanical behavior of the existing subway station in the construction process is analyzed,and then the key technical points and key points of the construction of the underpass project are put forward.(3)In order to ensure the safety and scientific rationality in the construction process of crossing the existing station project,in this paper,the overall control standard for the settlement of the existing subway station structure caused by the underpass construction is proposed,and the control standard for each stage of the construction process is given based on the displacement distribution principle.and the application of the fault tree method,Kent model method,real-time dynamic monitoring method,created a comprehensive range of reasonable risk identification,risk evaluation,risk monitoring and scientific risk timely response to the four stages,such as risk control process,to ensure the construction safety risk in the process of crossing the elaborating management,so as to ensure the safety of the crossing engineering reliability.(4)Through the induction and analysis of the field monitoring,the deformation and settlement law of the tunnel group under the existing station is obtained and the deformation of the track is analyzed.Finally,the theoretical calculation value and numerical calculation value are compared with the monitoring data to verify the scientific nature of the risk control of the crossing project.