高应力脆性岩石卸荷条件下时滞性破坏机制

Some major engineering apocalypses indeuced by deep underground brittle rock excavation sometimes do not happen instantaneously, often show time-lag effect failure behavior. This research project based on the construction of Southwest hydropower station, through the laboratory test, theoretical research and micromechanics numerical experiments, the forefront rock mechanical issues such as time-lag failure mechanism of deep buried brittle rock in condition of loading and unloading path and time dependent characteristic of strength are researched in detailed. Via static fatigue testing on different deviatoritic stress intensity factor conditions, simultaneously monitoring the crack incubation and propagation matching AE testing, the time-dependent crack evolution regulation and characteristics are obtained and the functional relationships of lag time to failure vs. the deviatoric stress intensity factor are established, with above further research to refine the mechanism of time lag failure of rock. Through embedding in micro cracks damage rate equation to bonded-particle model in PFC, reconstructed and set up a corresponding stress corrosion aging model and to realize; Finally based on the particle flow code, the the simulation method of lag time to failure and the stress corrosion process are proposed. Hence a new lab test and numerical test methods are initially formed for the long-term stability prediction of deep buried underground rock excavation, which has important theoretical and engineering application value.

深埋地下脆性岩体开挖卸荷诱发的重大工程灾变往往不是开挖瞬时发生的，有时表现出滞后效应。本课题依托西南水电站的建设，通过室内试验、理论研究及细观力学数值试验，对深埋脆性岩石在加、卸载路径下的时滞性破裂机制及其强度的时效特性等岩石力学前沿问题展开深入细致的研究，通过不同应力强度因子（偏应力强度比）下的岩石三轴静疲劳试验并匹配微裂纹孕育、扩展等过程的AE声发射活动监测，揭示加、卸应力路径下岩石强度及微裂隙的时效演化特征和规律，建立岩石滞后破坏所需时间与应力强度因子之间的函数关系，进而提炼脆性岩石时滞性破裂及强度时效性机制；通过在PFC颗粒接触本构模型中引入微裂纹损伤速率方程，重构并建立相应的应力腐蚀时效模型，从而提出基于颗粒流的脆性岩石滞后破坏时间及过程的模拟方法，初步形成一套地下深埋岩体开挖后围岩长期稳定性预测与评价的室内试验及细观力学数值模拟方法，具有重要的理论和工程应用价值。

依托锦屏二级电站工程，采用室内试验、理论分析和数值模拟相结合的研究方法，综合运用岩石力学、损伤断裂力学、地球物理学、声波波速与声发射监测及定位和岩样CT 扫描等理论与检测手段，通过开展高应力条件下三轴压缩破坏和三轴卸荷破坏试验研究，揭示了不同应力路径下破坏机制、非线性强度参数（剪胀角）等演化规律；通过岩石时效变形和时滞性破坏试验，获取脆性岩石破坏所需时间与破坏驱动应力水平之间的曲线关系；基于室内岩石高应力三轴卸荷条件下的流变试验成果，以损伤Burgers模型为基础，提出了一个改进Burgers 蠕变损伤模型。基于FLAC3D有限差分软件开展高应力下深埋洞室围岩开挖后损伤区和塑性破坏区演化的时效特性的数值模拟，为深埋隧洞围岩的稳定性预测、支护设计和工程处理措施的制定提供理论依据。