Study On The .Construction Technology Of Mining Excavation Of Middle Tunnel For Double-Deck Subway Station

At present, the subway stations constructed completely by mining excavation method and been put into operation in our country were Xidan station, Tianmen west station, Dongdan station and Wangfujing station in Beijing subway. The hole-column method, pile-column method and "double glasses" method were adopted to construct the above tunnels. The method of mining excavation of middle tunnel, with enormous constructing difficulties and great safety risks, was firstly applied in No.5 subway line of Beijing in the construction of domestic double-deck subway station. In this paper, the construction technologies of mining excavation of middle tunnel were studied through experimental research in detail based on the construction of Ciqikou station in No.5 subway line in Beijing. The technical difficulties such as excavation, system transition and controlling of the ground settlement etc. in the construction of double-deck subway station with large span were successfully solved. Using preact grouting to strengthen and improve strata, the safe excavation in the loose stratum with silty sand was achieved. Furthermore, owing to the reasonable partition and the scientific excavation procedures, we succeeded in reducing the constructing disturbance, controlling the ground settlement, ensuring the constrcting safety and accelerating the construction speed. Moreover, monitoring and measuring technologies were applied to guide in-situ construction. Through the monitoring data analysis, the quantitative analysis respecting to the influential zones of ground settlement, the temporal effect of deformation and the settlement ratio during all the excavation and lining phases were carried out. Accumulated technical parameters and construction experience are devoting to the future development and extension of subway construction.