深埋岩溶隧道劈裂型突水机理与防突厚度预测研究

The research project is aimed at water inrush mechanism of hydraulic fracturing style, in the process of excavating deeply-buried tunnel nearby water-filled and high-pressure cavities. Firstly, a series of physical model tests for water inrush of deeply-buried tunnel are done, and in this process the similar material between tunnel and cavity is divided into two kinds: unbroken material and material with cracks of different dip angles. Therefore, the characteristics of deformation and damage status for deeply-buried tunnel under outer load are acquired, and the influence of cracks of different dip angles on water inrush characteristic is analysed. And then, based on means of in-situ monitoring and theory analysis, multi-discipline research methods are used, containing unloading rock mechanics, damage mechanics and fracture mechanics. The characteristics of growth for microscopic cracks and formation for macroscopic fracture surfaces are researched. Besides, in the environment of high geostress, considering the influence of unloading and high water pressure, the crack initiation and propagation mechanism of unbroken rock and rock with cracks is studied. On these bases, water inrush mechanism of hydraulic fracturing style for deeply-buried tunnel nearby water-filled and high-pressure cavities is proposed. Finally, a new prediction model of outburst-prevention thickness is presented, combining least square support vector machines, genetic algorithm and numerical calculation. The proposed results will provide theory and application foundation for proper design and safe construction of deeply-buried karst tunnels, in highroad, railway and hydroelectric engineering for medium and long-term strategy planning of our country.

针对邻近高压富水溶腔深埋隧道开挖卸荷过程中劈裂型突水的发生机理，首先开展一系列隧道与溶腔间分别为完整相似材料与含不同倾角裂隙相似材料的深埋隧道劈裂型突水物理模型试验，获得外载作用下深埋隧道的变形破坏特点，分析隧道溶腔间岩柱中不同倾角裂隙对隧道突水特征的影响规律。进而基于现场监测和理论分析手段，采用卸荷岩体力学、损伤力学、断裂力学多学科交叉的研究方法，研究隧道劈裂破坏过程中细观裂纹发育与宏观破裂面形成发展特征；揭示高地应力环境中，卸荷与高外水压力联合影响下完整岩石与含裂隙岩石中裂纹的萌生、扩展机理。在此基础上，提出邻近高压富水溶腔深埋隧道劈裂型突水的发生机制。最后，综合集成最小二乘支持向量机学习方法、遗传算法优化技术和数值计算方法，建立岩溶隧道防突安全厚度预测模型。为我国中长期战略规划中公路、铁路、水电工程深埋岩溶隧道的合理设计和安全施工提供理论与应用基础。

针对深埋隧洞/隧道开挖卸荷过程中劈裂型突水的发生机理，首先开展了一系列高应力和高水压条件下的岩石卸荷试验，获得了不同外载条件下岩石的变形与强度特性，研究了高应力卸荷和高水压联合作用下岩石破坏过程中的细观裂纹发育与宏观破裂面形成特征。进而基于理论分析手段，采用卸荷岩体力学、损伤力学、断裂力学多学科交叉的研究方法，揭示了高地应力环境中，卸荷与高水压力影响下含裂纹岩石中裂纹的扩展机理，建立了隧洞围岩Ⅰ-Ⅱ复合型裂纹临界扩展判据的解析解，分析了裂纹不同倾角、长度、埋深等特征对隧洞围岩劈裂破坏临界条件的影响规律，导出了考虑卸荷和高水压力影响的隧洞围岩应力和塑性区半径表达式，提出了高水压力作用下裂隙岩体的水力劈裂破坏机制。最后，通过对某抽水蓄能电站引水隧洞充水过程中出现的劈裂破坏现象开展原因探索、机理分析和数值模拟验证，使研究成果应用于解决实际工程问题。本项目研究成果为公路、铁路、水电工程深埋隧洞/隧道的合理设计和安全施工提供了理论与应用基础。