The Numerical Simulation Of TBM Adjacent Tunnel Construction About Overlapped Subway

With the massive construction of subway in major cities, more and more closely overlapped tunnels will appear in the downtown or some specific areas due to the restrictions of urban buildings and to meet the needs of comprehensive development and utilization of the underground space. TBM adjacent construction of the overlapped subway is a very complex issue, which is influenced by many factors and these factors restrain each other. Moreover, the shield or TBM excavation was adopted in the most excavation of the subway. Therefore, the research on TBM adjacent construction of the overlapped subway is of great significance. This thesis selects Chongqing Metro TBM test section in the sixth line of the overlapping close-risk profile, using the parameters of the engineering survey and design and the tunnel and geotechnical engineering special software Midas/GTS for the TBM construction process simulation in order to analyze the following questions:(1) The thesis makes a summary of the domestic and international research status of the closely overlapped tunnel, highlights the basic principles of construction of the tunnel and the theories of numerical simulation, discusses the two-hole adjacent tunnel's several ways and their mechanical characteristics.(2) According to the survey and design parameters provided, this thesis aims to establish a three-dimensional finite element model by selecting the construction section of the nearest overlapped tunnel. This thesis simulates the process of TBM construction in the scheme of excavate the upper tunnel firstly and the scheme of excavate the belower tunnel firstly respectively by Midas/GTS software, analyzes the influence of ground settlement of surrounding rock stress and displacement of the change rule during the tunnel construction. It also analyzes the stress value of the tunnel lining structure and the change of displacement value, calculates the tunnel lining strength and finally analyzes the security of tunnel lining structure.(3) The conclusion can be drawn by the comparison of the two schemes:When two tunnels are excavated at the same time, it is reasonable to excavate the below tunnel first in terms of the changes of the ground's surface subsidence, the stress and displacement of surrounding rock and the stress and displacement of tunnel lining. In addition, the safety parameter of lining structure by calculating is bigger and TBM tunnel construction can be carried out safely.This thesis gets the reasonable schemes of overlapped tunnel construction by the simulates TBM construction process under different construction schemes. Therefore, it is a certain reference value for similar projects.