Calculation of surrounding rock pressure of large section underground excavation metro station based on the construction process

Abstract

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.

Improved Protodyakonov’s Method of the Tunnel Surrounding Rock Pressure under the Seepage Condition of Weak Interlayer

“…Wang studied the method used for calculating the small clearances of tunnels with large cross-sections. Based on the calculation result of the surrounding rock pressure obtained by the code method, the pressure of the surrounding rock is amplified, or the elastic resistance of the middle sandwich wall is reduced according to the influence law of the smalldiameter distance [15][16][17][18]. As the method used for calculating the surrounding rock loses pressure in a shallow tunnel, a new calculation model used for the surrounding rock pressure in the folded zone is proposed [19].…”

“…Sarfarazi et. al., Zhang et al, and Zhang and Qui reported that with the multifactor surrounding rock pressure calculation theory, the surrounding rock pressure of arbitrary shape and span can be easily calculated and analyzed, as well as its stability and safety [20][21][22]. Wen et al [23] introduced the weight coefficients of tunnel depth H, tunnel span B, internal friction angle φ, and rock weight γ and deduced the calculation formula of the surrounding rock pressure for extensive excava-tion of section tunnels.…”