Study On Stability Of Tunnel Excavation Face For EBP Shield Machine In Expansive Rock And Soil

At present, the research on the construction technology and construction technology of shield machine has become an important direction in the field of engineering, and the stability of the excavation face is a key technology. Reasonable excavation face support force design, not only can ensure the smooth progress of shield tunneling, but also can reduce the impact of construction on the surrounding strata and buildings. In our country, the expansive rock and soil are widely distributed, because of the engineering problems caused by the expansion of soil, it is very important to analyze the stability of the shield in the expansive soil.On the basis of summarizing the existing research results, this paper analyzes the stability of expansive soil and non expansive rock face by means of limit equilibrium method and numerical simulation method.The main contents include:(1)The finite element numerical simulation analysis software Abaqus. The plans were compared with the existing literature simulation design, verify the feasibility of this software analysis of tunnel excavation face stability. Establish without considering and considering expansive rock tunnel excavation model of expansive soil, by decreasing the excavation face support force, get the surface displacement and the corresponding point level corresponding to the excavation surface settlement center. Through the analysis of the excavation face supporting pressure variation of the minimum limit supporting force of the horizontal displacement of the center point. The sensitivity parameters of the tunnel are analyzed, and the influence of the depth of the buried depth, elastic modulus and cohesion of the soil on the limit support force of the expansive rock and soil excavation face is discussed. Preliminary study on the value of coefficient of expansion in expansive rock soil, and analyze the influence of water content and soil water content on the limit support force of expansive rock and soil excavation face.(2) The existing wedge model is summarized, the calculation formula of the ultimate minimum support force is derived by the limit equilibrium method, and the parameters are calculated and analyzed. A simplified three dimensional wedge model was put forward considering the expansive condition of rock and soil, and the parameters of the model were modified. Two comparison of the formula, it is concluded that the expansive soil is not conducive to the stability of the excavation face.(3) Combining with numerical simulation and analysis of the theoretical model of a construction section of Guangxi metro line to the actual engineering situation, both obtained results are close to each other and with the actual engineering normal supporting force are compared and analyzed.