岩溶隧道涌突水形成机制及岩壁安全厚度研究

Study on formation mechanism of water gushing in karst tunnel and safety thickness of rock wall

为了分析岩溶隧道涌突水形成机制,探讨防涌突水形成所需的最小岩壁安全厚度,基于莫尔-库伦判据探讨了爆破振动对围岩稳定性的影响,以振动加速度为指标推导了损伤区的分布范围;基于断裂力学理论分析了水力劈裂的启动判据,结合强度准则推导了裂隙带的分布范围;同时考虑施工爆破振动作用和高压水力劈裂作用,进一步分析了启动水力劈裂的条件;基于力学理论分析了隧道岩溶段施工过程中涌突水的形成机制,并提出防涌突水所需岩壁最小安全厚度的理论模型和计算公式。研究结果表明:防涌突水所需涌突水岩壁最小安全厚度由爆破严重损伤区、溶洞周边裂隙区、裂隙扩展区、潜在危险区四部分组成,案例的理论计算值与现场实际安全岩壁厚度值接近。研究成果可为中坝等隧道的安全施工提供依据。

This paper aims to analyze the formation mechanism of water breakthrough in karst tunnel and explore the minimum safety thickness of the rock wall required for preventing water gushing to provide basis for tunnel construction safety. The influence of blasting vibration on the stability of surrounding rock is discussed based on Mohr-coulomb criterion and the distribution range of damage area is derived by blasting vibration acceleration. The starting criterion of hydraulic fracturing is analyzed based on the theory of fracture mechanics and the distribution range of fracture zone is derived by combining strength criterion. Considering the effect of blasting vibration and hydraulic fracturing together,we analyze the starting criterion of hydraulic fracturing.The formation mechanism of water gushing during tunnel construction in karst section is analyzed based on the theory of mechanics and the theoretical model and calculation formula for the minimum thickness of the rocky layer are proposed. The research results show that the minimum safe thickness of rock wall for water bursting is composed of four parts： the blasting seriously damaged area,the crack zone around the cave,the crack expansion zone and the potential danger zone. The actual safety thickness value is closed to theoretical calculated value in the study case.