大凉山地区深埋高地应力公路隧道岩爆机理及防治对策

本文以乐西高速大凉山2号隧道工程为依托，对大凉山地区深埋高地应力公路隧道岩爆机理及防治对策进行研究。从深埋隧道岩爆孕育力学角度出发，结合能量及应力条件，运用有限元分析软件MIDAS-GTS-NX分别建立隧道在不同埋深、进深及断面形状的三维有限元模型，对围岩应力特征进行比较分析。研究结果表明：从力学角度来看，岩爆的孕育过程是由弹性转换为塑性，并发生在塑性岩体中，周围弹性岩体负责为其提供能量，围岩储存的能量和开挖导致的应力集中分别是岩爆发生的根本条件和触发条件；隧道埋深、进深以及断面形状是影响隧道岩爆的重要因素，其中埋深对其影响最为明显，围岩最大主应力与隧道埋深、开挖进深及断面大小呈正相关性；隧道埋深在600 m左右时，围岩最大主应力达到45.90 MPa。根据强度应力比法，结合施工钻孔取芯参数，最终结果表明大凉山隧道属于极高地应力区，具有发生岩爆的风险，施工时应当采取相关防范措施。

Rockburst Mechanism and Prevention Countermeasures of Deep Buried High Ground Stress Highway Tunnel in Daliang Mountain Area

Based on the Daliangshan No.2 tunnel project of Lexi Expressway, the rockburst mechanism and prevention countermeasures of deep buried highway tunnels with high ground stress in the Daliangshan area were studied and analyzed. From the perspective of rockburst incubation mechanics of deep buried tunnels, combined with energy and stress conditions, the finite element analysis software MIDAS-GTS-NX was used to establish three-dimensional finite element models of the tunnel at different depths, cross-section shapes, and the stress characteristics of surrounding rock were compared and analyzed. The results show that, from the mechanical point of view, the preparation process of rock burst is transformed from elasticity to plasticity and the rock burst occurs in plastic rock. The surrounding elastic rock is responsible for providing energy for it. The energy stored in surrounding rock and the stress concentration caused by excavation are the fundamental and triggering conditions for the occurrence of rock burst, respectively. The buried depth, excavation depth and cross-section shape are important factors affecting the rock burst of tunnel, among which the buried depth has the most obvious influence. The maximum principal stress of surrounding rock is positively correlated with buried depth, excavation depth, and cross-section size. When the buried depth is about 600 m, the maximum principal stress of the surrounding rock reaches 45.90 MPa. According to the intensity stress ratio method, combined with the construction drilling core parameters, the final results show that Daliangshan tunnel belongs to the extremely high ground stress area, which has the risk of rockburst, and relevant preventive measures should be taken during construction.