| With the development of China’s transportation and the continuous expansion of the urban size, many large cities have set off a wave of subway construction, in order to solve the increasingly serious urban traffic jam. While building a subway tunnel, the surface movement and deformation are inevitable, and these may do great harm to ground buildings, pile foundation and underground pipelines, etc. Because of the peculiar formation conditions, construction conditions and other differences in Changsha city, the problem of the ground settlement and the impact on the surrounding environment induced by shield tunnel excavation were particularly serious. Based on the project of Changsha No.2Metro Line, the paper has conducted researches on characteristics of ground surface settlement induced by EPB shield construction. The main ideas were as follows:(1) The paper analyzed the characteristics of the strata of Changsha No.2Metro Line and the influence on shield tunneling. Combined with formation conditions and shield tunneling parameters, various sections’ transverse surface and variation characteristics of the ground settlement as the EPB tunneling forward were discussed. By selecting70surface settlement data for statistical analysis, the paper had summarized the surface subsidence characteristics in different strata.(2) By using least square optimization methods and MATLAB program, the in-situ surface settlement values were selected to find out the best numerical-fitting peck formula, then anti-calculated the the initial value range of the ground loss ratio and width factor of ground settling tank, which could provide references to the follow-up construction.(3) Three-dimensional numerical analysis model of shield tunnel undercrossing Jingzhu Expressway was constructed for studying the surface subsidence characteristics. Compared with in-situ data analysis, the general characteristics of the ground settlement of shield tunnel undercrossing the highway were obtained. |
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