The traditional calculation method of the surrounding strata pressure of the tunnel does not consider the tunnel construction process. The excavation of the large-section tunnel mostly adopts the section excavation method, which is to excavate and support at the same time. The stress state of the pressure of surrounding strata changes gradually during the excavation process. The traditional calculation results of tunnel surrounding strata pressure are generally large. In this paper, the large-section tunnel is simplified into three parts, and the degree of influence (η1, η2, η3) of the excavation height h and width b of the advance pilot hole and the distance d between the advance and rear pilot tunnels on the surrounding rock pressure calculation are analyzed. The regression equation for calculating the influencing factors (tunnel depth H, tunnel span B, internal friction angle ϕ, and rock weight γ) of surrounding rock pressure (p) is established. Through the numerical analysis, the influence coefficient η is obtained, the weight coefficient is introduced, and the computing formula of the pressure of surrounding strata of the large-section tunnel excavation is derived. The formula is used to the computing of the pressure of surrounding strata with a large-section subway station and the correct conclusion is obtained.
With the large-scale application of urban comprehensive pipe gallery in China, it is an urgent engineering problem that how to adopt appropriate technical schemes for the foundation of comprehensive pipe gallery under different geological conditions. First of all, this paper starts from the unique stress condition of the comprehensive pipe gallery, through the analysis of the change of the stress on the foundation soil, it comes to the conclusion that the stress on the foundation soil becomes smaller after the completion of the comprehensive pipe gallery structure, and further analyses the influence of the buried depth and section size on the stress change of the foundation soil. Then, according to the foundation treatment scheme of the comprehensive pipe gallery in the collapsible loess area, some optimized suggestions and ideas are put forward, in order to provide more economical and simple foundation treatment measures for the construction of the comprehensive pipe gallery in the future.
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