岩溶隧道掌子面附近的高压富水溶腔易造成突水、突泥地质灾害，在施工中确定合适的岩墙厚度是一个亟待解决的技术问题。基于极限分析上限原理提出了两种新的岩墙厚度计算思路，即线性Mohr-Coulomb准则方法与非线性Hoek-Brown准则方法。根据构建的相应三维破坏模式，推导演绎了计算步骤，最终得到了这两种方法的岩墙厚度表达式。采用线性Mohr-Coulomb方法计算了Ⅰ～Ⅴ级围岩下的岩墙安全厚度。结果表明：随着围岩等级的逐级降低，即黏聚力、内摩擦角的减小，岩墙厚度在不断增大。对于非线性Hoek-Brown方法则分析了各个参数对岩墙厚度的影响，并根据计算结果绘制了岩墙的破坏形状与范围；同时，给出了Hoek-Brown常数A、B的建议取值，即围岩Ⅰ至Ⅵ级、岩性条件从好至坏，分别建议A取0.5～0.3，B取0.7～0.9。应用这两种方法分别计算了宜万铁路云雾山隧道与野三关隧道溶腔的预留岩墙厚度，与工程实际吻合良好，从而验证了方法的可行性。这两种计算方法可为今后高风险岩溶地区隧道的设计与施工提供参考。

The high pressure and water-bearing caverns close to the face of karst tunnels are liable to induce geological hazard of water inrush and mud outburst, therefore, the determination of appropriate rock wall thickness is a pivotal problem which needs to be solved immediately in tunnel construction. Two procedures, one with linear Mohr-Coulomb criterion and the other for the case of nonlinear Hoek-Brown failure criterion are proposed to compute the rock wall thickness based on upper bound theorem of limit analysis theory. According to the three-dimensional failure pattern established here, the specific procedures are deduced to derive the expressions of rock wall thickness with these two methods. The linear Mohr-Coulomb method is adopted to calculate the rock wall thickness under the surrounding rock ranging from levelⅠto Ⅴ. The results indicate that with the decrease of surrounding rock level, namely a lower values of cohesion and internal frictional angle, the thickness increases continuously. As to the nonlinear Hoek-Brown approach, the effect of each parameter on rock wall thickness is analyzed, and the failure shape and scope of rock wall are plotted based on the calculation results. Meanwhile，the suggested values of constant A, B in Hoek-Brown criterion are given. Namely, the surrounding rock changes from the level Ⅰ to Ⅵ, the lithologic condition ranging from good to bad，it is suggested to give A for 0.5~0.3 and B for 0.7~0.9. The rock wall thicknesses of Yunwushan tunnel and Yesanguan tunnel are calculated with two methods, respectively, and the results are in good agreement with engineering practice, which verifies the validity of the methods in this literature. The two methods could provide reference for the design and construction of tunnels in high-risk karst regions.