锦屏深埋大理岩破裂扩展的时间效应试验及特征研究

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。

Experimental research on time-dependent behavior of crack propagation in Jinping deep marble

The long-term stability of underground engineering is closely related to the time-dependent behavior in brittle rock.Jinping deep marble will appear initial damage when subjected to high stress unloading.The no damaged rock sample is obtained by sampling without damage and tested by acoustic emission.The effect of initial damage on test result is rejected.A series of long-term static-fatigue tests are carried out to test the time-dependent behavior of Jinping deep marble.The marble in Jinping shows the strength degradation with time.When the driving-stress ratio is rather lower,the failure time is longer.The static-fatigue limit is 0.48.The creep curve can also be divided into three phases when brittle rock under long-term loading and the strain ratio shows corresponding change trend.The deformation characteristics and failure mode in static-fatigue test are analyzed by dilatancy index.The stress relaxation zone and concentration zone caused by excavation are calculated by FLAC3D.The result indicates that the buried depth affects the test.When the rock samples contain joints,the strength is rather lower.Numerical test is performed by smooth joint model in the particle flow code(PFC).The numerical result meets well with the test.The existence of joints impacts the strength of rock.The rock will be compacted closely in initial loading stage and show the hardening effect and ductility behavior in residual stage.