岩溶隧道掌子面防突厚度理论分析

Theoretical Analysis on Water-resisting Thickness of Karst Tunnel Face

掌子面岩墙预留厚度是高风险岩溶隧道采用释能降压法施工时的一项重要技术参数。本文基于弹性厚板理论,分析了岩溶隧道掌子面突水机制,推导了边界条件分别为固支和简支两种模式的岩溶隧道掌子面岩墙安全防突厚度及临界水压计算公式。上述计算公式的参数化分析表明,两种模式下掌子面岩墙安全防突厚度随前方岩溶水压力、岩体泊松比的增大而增大;掌子面岩体质量越差,防突厚度愈大。临界水压力随掌子面岩墙厚度增加而增加,掌子面岩体质量越差,临界水压力愈小。掌子面岩墙安全防突厚度的理论分析及算例结果表明,固支边界条件下的计算结果与施工中普遍采用的预留厚度值较为一致,该结论可为类似工程提供参考和借鉴。

The reserved thickness of rock wall ahead of tunnel face is an important technical parameter for energy releasing and pressure reducing in karst tunnel with high risk construction. Based on Elastic Thickness Plate Theory,the water-inrush mechanism of karst tunnel face was analyzed,on the meantime,the formulas for calculating waterresisting thickness and the critical water pressure under the clamped support and simple support boundary conditions respectively. The parametric study of above formulas shows that the water-resisting thickness increases with the increased water pressure inside karst cavity before tunnel face and Poisson＇s of rock mass of tunnel face; The worse the quality of rock mass before tunnel face is,the smaller the critical water pressure is. The results of theoretical analysis of water-resisting thickness and calculation outcomes of sample demonstrate that the calculating value of water-resisting thickness by the formula under the clamped support condition is more consistent with the reserved value in actual projects,therefore,which can provide reference for similar engineering projects.