为减少岩溶隧道存在的突涌水灾害，对岩溶区隧道突涌水灾害形成机制和溶洞溶腔与隧道的3种位置关系（溶腔与洞轴线正交、斜交和平行）进行分析。以对应的隔水岩盘厚度要求最大（危险等级最高）的正交模式为例，采用数值模拟方法，分析隧道围岩级别、溶腔水压力、溶腔尺寸对隔水岩盘设计厚度的影响；通过对不同工况下岩溶隧道最小隔水岩盘进行对比分析，研究隔水岩盘厚度控制因素，推导出不考虑溶腔体积和考虑溶腔体积2种情况下的隔水岩盘最优设计厚度表达式。对圆梁山隧道DK354+460溶腔情况进行对比，结果表明利用本文公式计算得到的安全厚度值相对合理，该研究对实现岩溶区隧道隔水岩盘安全厚度科学预测提供了一种新的参考方法。

To reduce water inrush disasters in karst tunnels, the formation mechanism of water inrush disasters in karst tunnels and three positional relationships between karst caverns and tunnels (the cavity is orthogonal, oblique, and parallel to the axis of the tunnel) are investigated. Using the corresponding orthogonal mode with the largest requirement for the thickness of the waterinsulating rock disk (the highest risk level) as an example, the numerical simulation method is used to examine the effect of the tunnel surrounding rock grade, cavern water pressure, and cavern size on the design thickness of the waterinsulating rock disk. The minimum thicknesses of the waterinsulating rock disk of the karst tunnel under various working conditions are then compared to study the controlling factors of the thickness of the waterinsulating rock disk. Furthermore, the optimal design thickness expression of the waterinsulating rock disk with and without the consideration of the karst cavity volume is determined. Finally, results are compared with the situation of DK354+460 cavern in Yuanliangshan tunnel, and the results show that the safety thickness value calculated using the formula herein is relatively reasonable, which can serve as a reference for realizing the scientific prediction of the safe thickness of waterinsulating rock disks in tunnels in karst areas.