Analysis Of Soil Deformation & Soil-Structure Interaction With PBA Tunneling Method

With the process of urbanization in the world, cities around the world showed sharp traffic growth, which resulted in a series of problems, such as traffic congestion, frequent accidents and environmental pollution. All of these constrained urban development, and affected people's normal life. Rail transport had become one of the important means of relieving urban traffic congestion. With the development of subway construction, whose scale was growing, the surrounding environmental and other constraint factors were also increasingly so sharply, that the usable underground space was shrinking, the structure forms of metro stations and linking tunnels had been varied a lot, and the construction technologies had correspondingly gained much progress and been innovated. Many new construction methods had been successfully implemented and developed sharply. The PBA method for shallow buried underground excavated was one of them. Combining the advantages of the traditional shallow buried underground method and partial excavation with the characteristic of reverse construction method, the PBA method exhibits higher flexibility and wider adaptability. The PBA method obtained the success application firstly in Beijing subway Tiananmen west station, and then obtained large scale promotion in Beijing Metro Line Fu-Ba Wangfujing station, Line 4 Xuanwumen station and Huangzhuang station, Line 10 Suzhoujie station and Jinsong station, which proved that using the PBA method in loose soft soil for excavating shallow buried large section tunnels was practicable. Therefore it had broad prospect for application, and it was worth much promotion. But only theoretical analysis about the method was not adequate, and its mechanism and constraints of application were not yet fully understood, which may hinder further use and promotion in the underground engineering.Considering the above reason, firstly, this paper, based on the soil-structure model in the design theory of underground structure, and FDM(Finite Difference Method), with the aid of FLAC3D numerical simulation software, an analysis frame of construction process will be established, which is based on the characteristics of the PBA method. By analysis of the results, the change laws of soil deformation, and of ground stress, and of plasticity state of wall rock will be suggested. Secondly, based on load-structure model, this paper has analyzed the structure internal force change rules and the structure displacement change rules in each construction stage, using MIDAS-civil structure software. Finally, the article has summarized the PBA method, which is meaningful in theory for further application and promoting for similar projects.