| With its development and improvement, shield construction technology is more and more applied to the urban underground traffic engineering construction for its small impact, low construction environment requirements, rapid construction speed and high precision in construction. It has a vital significance for safety construction to maintain the stability of the working face during shield tunnel construction. Based on the limit support force of shield tunnel face as the research object, this essay mainly studies the following contents:1. This essay summarizes and generalizes the destabilizing forms of shield tunnel’s working force and theoretical research methods, introduces the yield criterion of destabilizing of shield working force, selects the Mohr-Coulomb yielding criteria to analyze the stability of the working force;2. Introducing and using the finite difference analysis software FLAC3 D to analysis tunnel working face stability calculation process, the essay has determined the limit support force of Gan river tunnel exploration in the period of composite soil excavation construction.3. The essay carried out the numerical analysis on the effects of tunnel buried epth,cohesion of strata, internal friction angle and the river water level on working force,obtained the influence of various factors on the supporting force.4. It combined the overlying soil pressure theory with Wedge theory to deduce to calculate the limit support force balance equation, and compared it with the results of numerical analysis.The innovation of the paper is based on Gan river tunnel engineering of Nanchang City, analyzed the limit of the supporting force when it is used in shield tunnel excavation of Nanchang area’s each soil layer, and the results is verified by using the limit equilibrium equation. |
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