| Based on Daping Tunnel of Xiang-Gui railway extension project, scheme comparison and selection is carried out using a variety of methods according to construction scheme of CRD method and three-stair seven-step method for large section tunnel in soft ground in this paper, so as to demonstrate the feasibility of three-stair seven-step method used in soft ground large section tunnel. The main research contents include:(1) Summarizing the development status, basic mechanical characteristics, existing research means and commonly used construction methods of soft ground large section tunnel, to pave the way for the study of construction technology of soft ground large cross section tunnel.(2) Combination with the site construction condition of Daping tunnel, the construction process and technology process of CRD method and three-stair seven-step method is discussed, and the selection principle of construction program of soft ground large section tunnel is proposed, and preliminary comparison and selection for two construction program is carried out.(3) Numerical analysis means is used to simulate the surrounding rock deformation and the supporting structure stress of different construction programs in soft ground large section tunnel, the characteristic of surrounding rock deformation and supporting structure stress is compared, and comparison and selection of two kinds of construction program is implemented.(4) Site construction condition, monitoring measurement results and construction control measures of Daping Tunnel are discussed, and site implementation effectiveness and the feasibility of CRD method and three-stair seven-step method are evaluated. |
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