四点弯曲试验条件下页岩的声发射特性

Acoustic emission behavior of shale under four-point bending test

利用PXWAE型声发射系统进行了四点弯曲试验条件下页岩的声发射试验研究,试验中记录了岩样所受的最大弯曲应力、弯曲应变、声发射事件数、声发射能量等多个参数。研究发现,垂直页岩层理施加荷载时,在四点弯曲试验条件下其凯塞效应是存在的,凯塞点可以直接通过应力与累计声发射事件数曲线得出;但受自身水平层理结构及局部破坏的影响,应变在受载过程中会发生松弛现象,不易直接由应变-声发射试验曲线判断出岩石的凯塞点,必须结合其它试验数据以及岩样的最终破坏形态综合判断。弯曲应力状态下岩石的声发射特性研究对于利用声发射技术进行矿区顶板或隔层的稳定性监测具有一定的工程指导意义。

PXWAE Acoustic Emission System is useol to investigate the acoustic emission behavior of shale under four-point bending test. In these tests, the maximum bending stress, bending strain, acoustic emission hits, acoustic emission energy and etc. , are recorded. The results show that when vertical loads impose on the shale sample which has horizontal stratification planes, Kaiser effect does exist under four-point bending tests. Kaiser point can be recognized directly from the stress vs. cumulative AE hits curve. But by the impact of shale＇s stratifications and local failure during the tests, strain relaxation occur which makes it difficult to determine the Kaiser point only by the strain vs. acoustic emission curve. An accurate conclusion can be achieved by a comprehensive judgment combing with all test data, as well as the failure mode of rock sample. The research on acoustic emission behavior of rock in the stress state during bending tests to some extend can provide guidance to engineering practice for stability monitoring of mine roof or separation layer with acoustic emission monitoring technology.