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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。
Karst tunnel near the face of the high pressure water-soluble chamber easily lead to water inrush, mud geological disasters, in the construction of the appropriate wall thickness is a technical problem to be solved. Based on the upper bound principle of limit analysis, two new methods for calculating the thickness of dykes are proposed, that is, the linear Mohr-Coulomb criterion method and the non-linear Hoek-Brown criterion method. According to the corresponding three-dimensional damage model, deduced the calculation steps, finally obtained the expression of the two methods of wall thickness. The linear Mohr-Coulomb method is used to calculate the safety thickness of rock wall under the grade Ⅰ ~ Ⅴ surrounding rock. The results show that the wall thickness increases with the gradual decrease of the grade of surrounding rock, ie, the decrease of cohesion and internal friction angle. For Hoek-Brown method, the influence of each parameter on the thickness of rock wall is analyzed, and according to the calculation results, the damage shape and range of the rock wall are plotted. At the same time, the proposed values of Hoek-Brown constants A and B are given, That is, rock Ⅰ to Ⅵ, lithology conditions from good to bad, respectively, recommended A 0.5 to 0.3, B 0.7 to 0.9. By using these two methods, the thickness of reserved rock wall of Yunwu Mountain Tunnel and Yeosanguan Tunnel of Yichang-Wanzhou Railway was calculated respectively, which is in good agreement with the actual project, which proves the feasibility of the method. These two methods can provide references for the design and construction of tunnels in high-risk karst areas in the future.