岩溶隧道顶板安全厚度的理论探讨与工程应用

在岩溶区隧道施工中，隧道顶部既有较大尺度溶洞引起的隧道顶板跨塌是威胁隧道施工的主要问题之一。从隧道施工引起的既有溶洞与隧道间岩层的受力，岩层力学性质和围岩水文地质条件变化出发，分析了隧道施工中影响岩层稳定的主要因素，在此基础上将隧道顶部既有较大尺度溶洞引起的隧道施工期顶板的破坏问题归结为两端简支或4边固支薄层岩板的失稳问题，建立了相应的力学分析模型。采用弹性板理论，对不同力学模型的受力状态进行分析，推导了建立在岩体抗拉和抗剪强度准则基础上的岩溶隧道顶板岩层最小安全厚度计算公式。采用该公式对武都水库导流洞既有溶洞影响下典型洞段隧道顶板稳定性进行分析，跟踪施工调查的顶板稳定情况性态验证了公式的适用性。

Theoretical study and engineering application of roof safe thickness of karst tunnel

Karst disaster is one of familiar geology disasters in tunnel construction in mountain area. The influence of concealed caverns on the stability of tunnel surrounding rock in tunnel construction in karst region is studied. The stability problem of tunnel roof under the influence of jumbo size concealed karst caverns is simplified to collapse destabilization problems of beam or plate. The analytical formula of the minimal safe thickness of karst tunnel roof is deduced on basis of elastic theory. The stability of tunnel roof in Wudu Reservior is analyzed by this formula; and the rationality and creditability of the formula is verified by in-situ test.