小三峡岩溶隧道围岩防突层安全厚度有限元分析

针对小三峡隧道岩溶发育的工程地质特征，采用有限元方法建立典型隧道断面数值计算模型，分析充水溶洞位于隧道不同方位、不同距离时隧道围岩位移和塑性区变化规律，并结合围岩的位移变化情况和塑性区分布情况作为评价隧道围岩突水的判据，得出防止隧道围岩突水的岩层最小安全厚度。研究结果表明：在岩溶水压力作用下，当洞径比一定时，随着溶洞逐渐远离隧道，溶洞对隧道的影响在逐渐减弱；当间径比一定时，溶洞直径越大对隧道的影响越明显；同时根据围岩的位移和塑性区计算结果得到了隧道围岩最小防突厚度。研究成果可为小三峡隧道安全施工提供技术支撑。

Finite element analysis on safety thickness of the inrush prevention layer in rock beds of the small Three Gorges karst tunnel

In view of the geotechnical characteristics of the karst in the small Three Gorges tunnel， the finite element method is used to establish a numerical calculation model of a typical tunnel section to analyze the variation laws of tunnel surrounding rock displacement and plastic zones when the water filled karst cave is located in different directions and distances of the tunnel. Then in combination with the displacement change of surrounding rock and the distribution of plastic zones， the minimum safe thickness of the rock layer to prevent water inrush from the surrounding rock of the tunnel is determined. The research results show that under the action of karst water pressure， when the cavity diameter ratio is fixed， the influence of the karst cave on the tunnel is gradually weakened as the cave gradually moves away from the tunnel. When the interval diameter ratio is fixed， the larger the diameter of the karst cave， the more obvious the influence on the tunnel. At the same time， according to the displacement of surrounding rock and the calculation results of plastic zones， the minimum inrush prevention thickness of the tunnel surrounding rock is obtained. The research results can provide technical support for the safe construction in the small Three Gorges karst tunnel.