| Xinle Ruins Station of Shenyang Metro is a Mining Station, which is constructed by Pipe-roof Pre-construction Method. Pipe-roof Pre-construction Method is an improvement on the basis of the formation Pipe-roofing Method. The steel pipe diameter can reach more than2meters in Pipe-roof Pre-construction Method. The soil is excavated inside the steel pipe manually or mechanically under the protection of jacking pipe. Then the steel pipe is cut, support structure is welded, and reinforced concrete structure is poured in the pipe. After strength and rigidity of reinforced concrete structure is attained, the soil under reinforced concrete structure is excavated and large cross section of underground space form. The most prominent feature of the construction method:through out the process, all of the excavation is completed after the pre-built and reliable structure, thus ensuring construction safety.Thus, the pipe jacking is a vital link in the construction method, which pre-manufactured a safe working space for follow-up process, thereby reducing the risk of construction. However, compared with the ordinary pipe jacking project, jacking pipe in this construction is with great particularity. Mainly reflected in the deep depth, full diameter, large quantity, and arranged in the form of complex. Based on Xinle Ruins Station of Shenyang Metro, the pipe jacking technology in the construction method is summed up, the interaction between the intensive full diameter steel pipe group and soil is focused on, as well as the environmental impact caused by the pipe jacking process and so on.The interactions between the intensive full diameter steel pipe group and the soil are of the following:(1) Combined with literature review and measured data of jacking force, the theoretical deficiencies of existing vertical earth pressure calculation is analyzed. New theoretical formula is got based on Terzaghi theory and M.M.PROMOJIYFAKONOV theory, and Matlab calculation program is written for jacking force calculation of the deep buried pipe. The calculation results show that the calculation results by the improved vertical soil pressure theoretical is less than that by Terzaghi theory and M.M.PROMOJIYFAKONOV theory, which is closer with measured results.(2) Combined with measured results, theoretical analysis of pipe axis offset and head deformation in jacking is proposed. It is proposed to carry out real-time monitoring of pipe axis by the pipe jacking stress monitoring, and proves the program is feasible by testing.(3) Based on knowledge of elastic mechanics and soil mechanics, theoretical analysis on the stability of the excavation surface is made in jacking.(4) Based on soil arching effect, optimum design method of the distance between pipes is put forward. Combined with this project, optimum distance is designed, and two kinds of optimization are got. Relative to the original program, the optimization program can save steel, shortening the time of the construction of the jacking, and can reduce repeated disturbance of soil in jacking.The environmental impacts caused by the pipe jacking process are of the following:(1) The surface settlement is caused by the dense jacking of full diameter pipes group. By the measured and theoretical study, it indicates that surface settlement is mainly caused by the loss of soil in jacking and groundwater seepage. Supporting and retaining of existing pipe will limit the downward displacement of soil, and greatly reduce the surface settlement caused by new pipe, so the surface settlement caused by the loss of soil in jacking is generally small, and no more than the value of the settlement alert. Surface settlement caused by groundwater seepage is much larger than that caused by the loss of soil. So serious groundwater seepage can cause much larger surface subsidence than the alert value.(2) According to the distance between rigid pipe and the jacking pipe, the impact is divided into two types:far-impact and close-impact. Based on the Winkler elastic foundation beam theory, the calculation method of the displacement, rotation, bending moment and shear of existing rigid pipe by jacking is proposed. And Matlab calculation program is written for the calculation of displacement, rotation, bending moment and shear. Combined with pipeline failure criteria, the stability can be determined easily.(3)In the construction method, grouting has three purposes:friction reduction in jacking, uplifting of surface, and reinforcement. Grouting in pipe jacking is researched, and effect of all kinds of grouting is analyzed.Parts of the research results in this paper have been used in Xinle Ruins Station of Shenyang Metro.
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