砂岩单三轴压缩过程中声发射特征的试验研究

Experimental Study of the Characteristics of Acoustic Emission for Sandstone Specimens Under Uniaxial and Triaxial Compression Tests

利用RMT-150B岩石力学试验系统,对义马曹窑煤矿顶板砂岩进行单轴、常规三轴和三轴卸围压试验,加载同时进行声发射检测.试验结果表明,岩样压缩变形破坏过程中的声发射参数与加载方式有关.单轴压缩时,各个阶段均有不同程度的声发射事件,声发射事件较为强烈,累计计数和能量明显偏高;常规三轴压缩时,岩样屈服前声发射事件较少,屈服阶段声发射事件逐渐趋于活跃,峰值后破坏阶段仍会产生部分能量较强的声发射事件,且围压越高破坏阶段持续时间越长,声发射特征表现越弱;三轴卸围压时,在卸围压前岩样声发射事件相对较少,卸围压过程中声发射事件逐渐趋于活跃,计数和能量大幅度增大,峰值后应力急速跌落到最低时,声发射事件迅速减少,声发射累计计数和能量基本保持不变,卸围压时岩样的失稳破坏更具突发性.

Uniaxial and triaxial compression tests and triaxial unloading confining-pressure tests for roof sandstones form Caoyao Coal Mine,Yima Coal Group,were carried out with a servo-controlled test machine RMT-150B,and the acoustic emission（AE） detections were conducted at the same time.The results indicate that there are different AE events in various conventional compression tests.AE events are different during uniaxial compression tests,but totally high in energy and accumulation number.During triaxial compression tests,AE events are less before specimens yielding,and gradually increase after specimens yield;AE events with a great deal of energy are still created in the process of friction slippage of specimens while their stress after peak value sharply decreases.The AE events for specimens are very intensive,their accumulative counts and energy are obviously high in uniaxial compression tests.The higher the confining pressure for specimens is,the weaker the AE characteristic parameters are.The AE events are comparatively less before unloading confining-pressure,gradually become more active in the process of unloading confining-pressure,which the counts and energy of AE events greatly increase.When the stress after peak value on specimens sharply decreases to the lowest,then the AE events will reduce rapidly,but the total counts and energy of AE events are basically the same.Specimens break unstable during unloading confining-pressure tests,but their unstable fractures are more possible to outburst.