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In this century, urbanization has entered a new developing period, either in quantity or scale of the city has a great increase . But with the urbanization appears the urban syndrome based on population and traffic congestion. In order to solve this situation, each big city energetically build subway lines. Along with the development of technology of construction, the construction method of subway station is constantly improved. The open cut method, subsurface excavation method, the cover-excavation method are widely applied in engineering. The choice of construction method is an important problem of the technical personnel concerned. More and more deep excavat- -ion emerged due to the the metro construction. Many stations are built in dense urban building areas,the underground pipeline are complex.During the excavation,surrounding environment must be strictly controlled.(1)This paper describes the open-cut method, subsurface excavation method and cover excavation method and application conditions of the construction process, combined with the May Fourth Square subway station in Qingdao hydrogeological conditions, traffic conditions, pipeline inbuilt situations, analyzed specific the feasibility of digging reverse construction from several aspects.(2)Analyzed the theory of space characters by the subway station excavation, in light of the blasting noise, shock wave and blasting vibration,studied the environmental impact of blasting, in this put forward the proposed control measures.(3)In this paper, based on a large number of theoretical and practical investigations, in the light of underground engineering, rock mechanics, computer science, information technology,used FLAC3D numerical analysis software to simulate each step of the construction; analysed ground settlement, the displacement on the top of pile, bottom uplift and the impact of the surrounding environment and its structure caused by foundation excavation on the principle of safety, practical applications and flexibility . Ensure safety and, ultimately, good economic returns, social and environmental benefits. (4) Has been studied the key technology in the process of the cover down excavation-mechanical analysis of vertical support structure, obtained by the force of the vertical support structure and the overall model can be simplified model to analyze, support columns and retaining pile occurs differential settlement capable of the weight、the upper load、positive and negative friction resistance,the internal force increases linearly with the increase of differential settlement, and finally put forward some specific measures to control differential settlement.
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