深埋大型地下洞室群硬岩EDZ动态演化过程研究

Rock burst, spalling, unravelling, distributed damage, large deformation, shear failure and collapse have been observed in deep buried large underground caverns, which is far beyond traditional recognition of failure mode driven by gravity. How to evaluate and predict the excavation damage zone (EDZ) in deep large caverns, especially in hydropower engineering, is becoming an urgent scientific issue. Based on four underground powerhouse projects, the modes, distribution and evolution of EDZ in homogeneous massive granite and anisotropic layered limestone rocks are selected to be studied. Structure and deformation of rock mass are investigated through the fine sampling and statistics of discontinuities. Based on the monitoring data of displacement, acoustic wave and acoustic emission, as well as the utilization of borehole images, the initiation stress, the mode, distribution and its progressive of EDZ are investigated. According to the unconfined and triaxil compprision tests, damage mechanics and acoustic emission tests in the laboratory, the initial cracking strength, damage strength, peak strength and residual strength are to be determined respectively. The brittleness-ductility-plasticity features which depend on the curves of the strain and stress at the difference confining pressures are to be defined. A compound strength criterion of surrounding rock in the condition of low confining pressure caused by excavation, and of high confining stress under natural stress, will be studied. The EDZ evolution under excavation in different rock mass structure, in situ stress condition and cavern characterization are analyzed by employing FLAC/PFC coupling method. The research achievement could be usefull for the design and construction of deep-buried underground caverns, and make some contribution to the development of rock mechanics.

在开挖深埋大型地下洞室群中出现了岩爆、片帮、张裂、剪裂、损伤、大变形或塌方事件，超出了重力驱动型破坏的认知范畴。及早评价因开挖而产生的围岩损伤规律成为如水电工程中亟需解决的关键科学问题。拟依托4个水电站地下厂房工程，研究均质块状花岗岩岩体、各向异性层状灰岩岩体在开挖过程中，硬质围岩的EDZ模式、分布及其演化过程。通过结构面采样和精细调查，把握岩体结构和围岩宏观变形破坏现象；通过位移、声波、AE监测和钻孔图像，把握EDZ的模式及其分布动态变化；基于精确室内强度和AE实验，确定岩石的起裂、损伤、峰值和残余强度，应力~应变关系随围压而变化的脆-延-塑转换特性；探索低围压~高围压应力状态下围岩EDZ分布；运用FLAC/PFC耦合方法，分析不同岩体结构、地应力、洞室特征、开挖因素等条件下随开挖EDZ的动态演化规律。成果可为深埋大型地下洞室群的建设提供理论支撑，丰富岩体力学研究内容。

鉴于我国水电资源主要集中在地质条件异常复杂的高山峡谷区，具有构造应力大、卸荷作用强、地震烈度高等特点，受各种因素制约，绝大多数水电站的引水发电系统都采用地下结构形式。在高地应力、强卸荷、地震烈度高等复杂地质环境中修建大型地下洞室群面临巨大挑战，如洞室围岩松弛深度大、位移量级高、塌方、岩爆、岩体深部拉裂等。深埋大型洞室群的围岩损伤止裂、变形控制、塌方处治等具有难度大、成本高的特点。认清地下洞室围岩开挖扰动（损伤）区的演化规律，对于优化支护参数、安全施工及评价工程稳定性和安全性至关重要，具有重要的现实意义和理论价值。因此对于高地应力、超大型规模等复杂地质环境下洞室群的围岩EDZ动态演化机制急需进行深入研究。本研究以在建的四座水电站地下厂房洞室群为研究对象，以工程地质学、岩石力学和损伤力学等理论为指导，结合一系列室内岩石力学试验和现场监测检测资料对开挖过程中洞室围岩出现的大量变形破坏现象以及围岩松弛深度过大等问题进行研究，归纳出了深埋大型地下洞室群围岩EDZ模式、分布和动态演化规律；给出了切合我国工程实际的经济有效的EDZ判别方法体系；给出了EDZ的强度判据和岩石强度参数估算、演化研究方法。