Research On Impact And Safety Control Measures Of Newly Built Subway Tunnel Undercrossing The Existing Subway Station

After entering the 21 st century, the economy of our country has increased rapidly, the urbanization construction and the urban population are growing quickly, especially the first-tier cities like Beijing, Shanghai, Shenzhen, it has brought the huge challenge to urban traffic. To ease traffic congestion problem, major cities are to invest in the construction of underground transit. Subway tunnel tend to be through the downtown district of the city, it will bring a lot of construction problems, the research of the tunnel crossing has an important significance on the rapid development of urban rail transit. This paper is based on a new subway tunnel in Beijing down-traversing the existing subway station engineering, combined with the domestic and foreign scholars’ research of the influence of tunnels crossing directly underneath on the existing structure and the construction methods and technology adopted in the construction of subway tunnel in our country, the main research content of the following aspects:(1) The construction of the subway tunnel according to the grade of surrounding rock, structure size, engineering situation, surrounding environment, schedule and cost factors can use different excavation construction methods. the Beijing region, this paper compared the commonly used three kinds of mining method with three dimensional numerical simulation analysis, namely the CRD method, the benching tunneling construction method(reserved core soil) and the whole section excavation method, respectively study the influence of the new tunnel under the three methods in the construction on the vertical deformation of the structure of the existing station hidden digging section; Then from the vertical deformation, the horizontal deformation and structure stress of existing structures, compare and analyze the numerical simulation results of three methods of construction, summarize that what kind of method of minimal impact of existing structures were least.(2) A new tunnel down-traversing the existing station in practical engineering should be grouting reinforcement on the surrounding soil, this paper adopts the benching tunneling construction method(reserved core soil), on the basis of construction, according to the different grouting range is divided into four kinds of condition, study the influence of the construction of the new tunnel under each working condition on both the existing structure deformation and the force.(3) Tunnels using mining method in engineering construction should strictly follow the guidelines of 18 letters, of which "short footage" is a very important one. This paper simulated tunnel respectively by 1 m, 2 m and 4 m of the three excavation footage, contrast analysis of deformation and stress of both the structure above the tunnel, to explore the influence law of different excavation on its.(4) Make collection of monitoring data at the project construction site, statistics the surface subsidence monitoring stations and the vertical deformation of existing structures, analysis of the typical monitoring deformation law in different construction stages, then make comparison between the deformation law and the numerical simulation, verify the correctness of the numerical simulation.