基于剪切破坏的深长隧道掌子面隔水岩层安全厚度的研究

A study of the safety thickness of water-resisting rock strata in a deep-buried and long tunnel based on shear failure

突水是复杂地质区域隧道修建时常见的地质灾害。掌子面前方隔水岩层是阻止突水发生的重要安全屏障。本文主要对隧道前方隔水层临界安全厚度的确定方法进行研究。首先基于Mohr-Coulomb破坏准则构建了隔水岩层剪切破坏力学分析模型并得到相应的隔水岩层安全厚度的计算公式;其次,对于深埋隧道,构造应力场对水平应力影响更明显,通过理论分析以及安全性角度分析,发现利用竖向应力计算法向应力更合理;然后,考虑隧道开挖对初始地应力的影响,对上述模型做了进一步的改进;最后,结合跃龙门隧道工程突水灾害的特点,利用区间非概率可靠性以及概率分析两种方法对隔水岩层厚度进行分析,并与现场实测结果进行对比验证。工程案例应用结果表明本文所提出的计算模型是有效的。本文的研究成果既是对现有的临界隔水岩层厚度的知识体系进行补充和完善,也可为后续的风险评估、风险对策的制定提供辅助信息。

It is a common geological hazard for water inrush when tunneling in a complex geologic area.The water resisting rock strata in front of a tunnel face is an important safety barrier to prevent the water irnush.This paper mainly studies the method of determining the critical safety thickness of the aquifuge in front of the tunnel.Based on the Mohr-Coulomb failure criterion,a shear-damage mechanical analysis model of the water-resistant rock layer is constructed and the corresponding calculation formula for the safety thickness of the water-resistant rock layer is obtained.For deep tunnels,the effect of the structural stress field on the horizontal stress is obvious.Through theoretical analysis and safety angle analysis,it is found that the calculation of the normal stress from the vertical stress is more reasonable.Considering the influence of tunnel excavation on the initial ground stress,the above model is further improved.Combined with the characteristics of water inrush disaster in the Yuelongmen tunnel project,the safety thickness of water-resistant rock stratum is analyzed by using two methods,which are interval non-probabilistic reliability and probability analysis,and the calculated results are compared with the actual field test results.The application results of engineering cases show that the calculation model proposed in this paper is effective.The research result of this paper is not only to complement and perfect the existing knowledge system of the critical water resisting strata thickness,but also to provide auxiliary information for subsequent risk assessment and risk countermeasure formulation.