Study On The Stability Of Deep Excavation Bracing By Soil Nailing Based On Indeterminate Method

In this paper, the stability of deep excavation bracing by soil nailing is studied by using indeterminate method, especially considering the three kinds of indeterminacy in deep excavation bracing by soil nailing: randomness, illegibility and grayness. By introducing fuzzy random reliability analysis method, the inner stability of soil nailing was analyzed, and fuzzy reliability as the index to evaluate the stability of deep excavation bracing by soil nailing was put forward. Combined with the engineering example, the gray system theory was applied to predict the deformation and its developing trend of deep excavation.The work mechanism of soil nailing in deep excavation was presented in this paper. On the basis of in-situ test, the author focussed on studying the pull-resist mechanism of soil nailing and the cohesible performance between nail and soil, and summarized the research results obtained by determinate method on work characteristics of soil nailing.On considering some drawbacks of the safety factor method, by taking into account the randomness of the distribution of the characteristics of soil in space and the effect of diversified loads and the illegibility of safety rules, the fuzzy random reliability method was applied to analyze the inner stability of soil nailing in deep excavation for the first time. The author deduced its fuzzy random limit state equation and calculated the fuzzy failure probability according to the JC method.As we know, the breakage of soil nailing is gradual and the construction of deep excavation is dynamic, the author established the GM(1,1) model based on gray system theory and accomplished the corresponding computer program. According to the limited deformation data and the program, we could predict the future deformation and its developing trend of soil nailing in deep excavation for the later construction, and set up the failure criterion of soil nailing to forecast the possible dangers in time. The precision of the model was validated by engineering examples.