圆形隧道环向存在隐伏充填溶腔时防突岩墙的上限稳定性分析

岩溶隧道施工中遭遇高压充填溶腔时，若防突岩墙的稳定性不足易造成突水突泥等地质灾害.因此基于极限分析原理提出了一种分析防突岩墙稳定性的研究思路.针对隧道环向遭遇隐伏充填溶腔的工况，利用广义切线法获得Hoek-Brown非线性破坏准则的转化强度参数，构建了岩墙二维计算模型.并结合上限原理与强度折减技术，将安全系数引入能耗分析过程，达到了表征防突岩墙稳定性的目的.最后，通过优化分析，探讨了岩墙安全系数随各参数的响应情况.研究结果表明：除围岩重度参数外，岩墙厚度、溶腔充填物压力、隧道支护压力、圆形隧道断面直径、单轴抗压强度、Hoek-Brown常数等，都对岩墙安全系数的变化影响显著.此外，将方法应用至“宜万铁路”、“忠垫高速”和“恩来高速”的岩溶隧道中，良好的结果验证了方法的可行性.
When the construction of tunnels encounters with the filled Karst cave, the instability of confining rocks normally causes the geological hazards like water or mud inrush. Based on the limit analysis theorem, a calculation method to investigate the stability of confining rocks was proposed. In view of latent filled karst cave existing in the circumferential direction of the tunnel, transformed strength parameters of Hoek-Brown nonlinear failure criterion were obtained by virtue of the generalized tangent technique, and the two-dimensional model was constructed as well. In order to characterize the stability of the confining rocks, safety factor was introduced into the energy dissipation analysis on the basis of upper bound theorem and strength reduction technique. The variations of safety factor with respect to the diverse parameters were then discussed through optimization analysis. The computed results show that the parameters, including thickness of rock plug, pressure in Karst cave, tunnel supporting pressure, diameter of the circular cross section, uniaxial compressive strength, and parameters of Hoek-Brown failure criterion had significant influence on the variations of safety factor. And it is found that the safety factor was insensitive to the change of unit weight of surrounding rock. Moreover, the proposed method was applied to engineering projects, and reasonable results were obtained, which verified the validity of the proposed method.