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脆性岩石破裂扩展的时间效应与地下工程的长期稳定性密切相关。针对锦屏深埋大理岩易受高应力卸荷而产生初始损伤的特点,首先利用无损取样技术获得无损岩样,并利用声发射对无损岩样进行初始损伤检测,剔除初始损伤对试验结果的影响。之后利用获得的无损岩样进行一系列的长期加载的静态疲劳试验验证锦屏大理岩强度的时效特性。结果显示,锦屏大理岩表现出强度随时间衰减的特性,当应力驱动比较低时,需要的时间也相应增加,最后得到静态疲劳极限为0.48。分析证明,脆性岩石在稳定荷载作用下蠕变曲线也分为3个阶段,同时应变率也表现出相应的变化趋势,利用扩容指标阐述了岩样在静态疲劳试验中的变形特征和破坏模式。最后,利用FLAC3D计算了开挖引起的应力松弛区和应力集中区,说明了埋深对试验结果的影响。针对试验中出现的含节理岩样强度较低的问题,借助颗粒流程序PFC中的光滑节理模型进行了数值试验,结果显示,节理的存在极大地影响了岩样的整体强度,并且在加载初期,存在压缩紧密,而在残余阶段,存在一定的强化效应和延性特征。
The time effect of the propagation of brittle rocks is closely related to the long-term stability of underground engineering. According to the characteristics of Jinping buried marble vulnerable to high stress and unloading, the non-destructive sampling technique is used to obtain the non-destructive sample and the initial damage detection is performed on the non-destructive sample using acoustic emission. The initial damage is excluded from the test results influences. After that, a series of long-term static fatigue tests were performed on the non-destructive rock samples to verify the aging characteristics of Jinping marble. The results show that the Jinping marble shows the decay of strength with time. When the stress is low, the time needed increases accordingly, and finally the static fatigue limit is 0.48. The analysis shows that the creep curves of brittle rock under steady load are also divided into three stages, and the strain rate also shows the corresponding trend. The deformation characteristics and failure modes of rock specimens in static fatigue test are expounded by the expansion index. Finally, the stress relaxation zone and the stress concentration zone caused by excavation are calculated by FLAC3D, and the influence of depth on the test results is illustrated. Aiming at the problem of lower strength of rock samples with joints, the numerical experiment is carried out with the help of the smooth joint model in the particle flow program PFC. The results show that the existence of joints greatly affects the overall strength of rock samples, , There is compact compression, and in the residual phase, there is a certain strengthening effect and ductility characteristics.