The Failure Characteristics of Granite under True Triaxial Unloading Condition
The brittle failure (rock burst) of rock is generally triggered by excavation under high stress in hard rock mass with the characteristics of local violent failure due to a large amount of elastic energy release suddenly around the surrounding opening. For better understanding and monitoring the behavior of hard rock, we have done a series of experiments on samples of Laizhou granite to simulate brittle failure of rock under excavation. Deformation and acoustic emission (AE) were monitored during the tests, which were conducted in a static servo electro-hydraulic controlled true triaxial test machine at a loading rate of 0.5-l.OMPa/s in three directions and an unloading rate of 30MPa/s on one side of the samples. The failure characteristics include thin spalling and slabbing due to tensile stress, blocky fragments with irregular shapes dominated by to shear stress or their coupling effect. The authors observe the slabbing or irregular blocky fragments for granite is closely related to the stress path and the boundary conditions, the higher stress before unloading, the more blocky fragments generated after unloading. The existence of free boundary of the rock mass is of benefit to form slab structure near the opening under a certain stress state to permit the stress redistribution in a period of time. Violent increase of AE events is an indication of rock failure. The testing results are indicative of the failure nature of this granite rock which implies stress mitigation is one method to decrease the disasters caused by brittle failure of rock mass due to excavation in deep underground engineering.
brittle failure stress path slabbing and buckling true triaxial unloading acoustic emission
MIAO Jinli JIA Xuena CHENG Cheng
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China State Key Laborator State Key Laboratory for Geomechanics and Deep Underground Engineering, Beijing, China
国际会议
The First International Symposium on Mine Safety Science and Engineering (首届矿山安全科学与工程学术会议)
北京
英文
47-52
2011-10-27（万方平台首次上网日期，不代表论文的发表时间）