Analytical Method for Surrounding ROCK Pressure of Shallow-Buried Double-Arch Tunnels Under Variable-Slope Ground Surfaces

Based on limit-equilibrium theory, a calculation method for the surrounding rock pressure of shallow-buried variable-slope arch tunnels is proposed. A calculation model for surrounding rock pressure of variable-slope surfaces is established according to the structure and stress conditions of shallow-buried arch tunnels, analyzing the geometric relations of the surrounding rock slope and calculating the area of each slope to obtain the expression for the slope’s weight. The thrust around the tunnel is derived from the limit-equilibrium state of the surrounding rock, leading to the calculation formula for the surrounding rock pressure of shallow-buried variable-slope arch tunnels. By comparing the measured data on surrounding rock pressure from the Laimipo Tunnel with the recommended calculation methods in standards, the rationality of the proposed method is validated. The conclusions indicate the following: (1) Introducing several variable-slope points into the traditional linear slope arch tunnel surrounding rock pressure calculation model can effectively adapt to different slope forms. (2) Example validation shows that the introduction of variable-slope points can effectively avoid the result errors caused by the traditional linear slope surrounding rock pressure calculation model. (3) When comparing the surrounding rock pressure calculation method proposed in this paper with the recommended method in standards, the results show that the maximum error of this paper’s calculation method compared to the measured values is 17%, indicating that the calculation method for surrounding rock pressure presented in this paper provides a reasonable estimate.