初期支护结构对高地应力隧道硬岩微震活动性影响的机理研究

At present, the microseismic monitoring technology developed in the deep tunnel of high ground stress is mainly used in the monitoring and warning of surrounding rock failure. When the micro-seismic activities of surrounding rocks tend to be active, the situation of "rigid and strong" support structures to deal with the potential failure often occurs in tunnel engineering. This will inevitably have an impact on the micro-seismic activity and the development of surrounding rock disasters. Therefore, the actual engineering has not really made use of the law of micro-seismic activity to guide the construction process and reasonable support design, and it is also necessary to explore the mechanism of the influence of the supporting structure system on the micro-seismic activity of tunnel surrounding rock. Based on this, this project will use the methods of experimental test, theoretical analysis and numerical simulation to study the influence mechanism of initial support structure on the micro-seismic activity of tunnel in hard rock and high ground stress. The relationship between the micro-seismic activity of surrounding rock and the mechanical effect of supporting structure will be discussed. The evolution law of micro-seismic parameters during tunnel brittle failure under the joint action of supporting structure and hard rock will be proposed. The above research is of great theoretical significance and practical value for the rational design of tunnel supporting structure system and effective prediction and prevention of surrounding rock disaster, which provides technical reserve for the future construction of a series of deep buried long tunnels in our country.

我国重大建设工程涌现出越来越多的深部隧道与地下工程。当前，在深部高地应力隧道开展的微震监测技术主要应用于围岩破坏及灾害的监测预警。由于施工人员畏惧高地应力岩爆灾害，在实际工程围岩微震活动很活跃时常采用“刚和强”的支护措施应对岩爆风险段。这与高地应力岩爆段应采用柔性支护的原理相违背，“刚和强”的支护必然对围岩微震活动和灾害孕育机制产生影响。基于此，本项目运用现场实验测试、理论分析和数值模拟方法，研究初期支护结构对高地应力隧道硬岩微震活动性的影响机理，探讨围岩微震活动与支护结构力学效应的相互关系，揭示隧道初期支护结构与硬岩共同作用下围岩脆性破坏的微震参数演化规律，提出基于围岩微震活动性的高地应力硬岩隧道初期支护对策。研究成果对合理设计高地应力隧道支护结构体系、隧道岩爆灾害的有效预测和防治具有重要的理论意义和应用价值，可为我国“深地开发”战略面临的一系列深埋长大隧道工程的建设提供理论和技术储备。

项目以我国重大建设工程中的深部隧道与地下工程为项目依托，主要研究了不同刚度隧道初期支护对围岩微震活动性的影响机理、隧道初期支护动态调控对围岩微震活动性的影响机理、高地应力硬岩与支护结构共同作用下隧道围岩脆性破坏的微震参数演化规律并基于深度学习算法（CNN、LSTM等）对微震多参数预测研究、基于围岩微震活动性的高地应力硬岩隧道初期支护对策。研究发现刚性约束使围岩在卸荷过程不能充分发挥自承能力，改变了应力调整活动，围岩破裂活动趋向能量积累和能量转移，岩爆发育周期延长，期间内微震事件数量增加，应力调整阶段微震事件呈现较小的能量释放和较大的震源变形，对应小能量事件比重增加和小体积事件比重减少；结合围岩卸压爆破探讨从隧道横向纵向切应力峰值的减小以及损伤区域的变化以及损伤值的减小得出了围岩卸压爆破有降低岩爆的效果，同时对比得出了围岩卸压爆破对隧道轮廓非开挖岩体损伤区域的影响；高地应力硬岩与初期支护共同作用下岩爆和塌方灾害都有独特的发育过程和微震前兆特征。该项目通过对初期支护结构对高地应力隧道硬岩微震活动性影响的机理研究，探索和揭示了高地应力隧道硬岩破坏过程微震活动特征的支护结构效应以及硬岩与支护结构共同作用下围岩破坏的微震参数演化规律及前兆预警判据。利用这些规律，可帮助认识支护结构影响下围岩破裂活动的特征、机制与阶段划分，建立支护结构影响的围岩破坏前兆预警判据，进而实现以科学合理的支护方式遏制岩爆等地质灾害的风险。随着川藏铁路、沿江高速公路等工程的开工，将会有一大批深埋、大、长隧道出现。但是这些沿线重大的工程地质问题复杂，因此隧道在建设过程中将会出现很多如岩爆、大变形、坍塌等地质灾害。其中以岩爆灾害最为突出，例如川藏铁路雅安至林芝段可能会发生岩爆的里程合计为169.88km（数据来源铁二院）。该项目成果可以有效促进这些重大工程中岩爆灾害防控理论、预警预报方法的创新和进步，为其建设提供理论和技术支撑。