三轴循环加卸载作用下煤样的声发射特征

Acoustic emission characteristics of coal specimen under triaxial cyclic loading and unloading

利用RMT-150B岩石力学试验机对煤样进行常规三轴、三轴循环加卸载作用下声发射试验,对不同加载条件下煤样的声发射特征进行分析。分析结果表明:在常规三轴压缩过程中声发射能量、累计计数和累计能量随时间变化趋势基本一致,均能较好反映煤样内部的破坏过程;在煤样循环加卸载过程间隔出现声发射信息,其能量、计数和幅值变化趋势一致,与煤样所受应力相吻合;煤样在常规三轴和循环加卸载破坏过程中声发射突变点在峰值应力的85%左右,可以作为判定煤样破坏的前兆;在循环加卸载过程中Felicity效应较明显,Felicity比值FR远小于1,随着循环应力水平提高,FR值不断降低,表明循环加卸载过程中声发射记忆具有超前特征,Kaiser效应的记忆效果较差,Kaiser效应作为煤体稳定性指标需谨慎。

By using RMT-150B rock mechanics test equipment,the acoustic emission（AE）tests of coal specimen under conventional triaxial and triaxial cyclic loading and unloading were carried out, and AE characteristics of coal specimens under different loading situations was analyzed. The test results show that the AE mutation point in conven- tional triaxial compression process is substantial in about 85 % of the peak stress, and AE count more accusatively responses to AE information in coal specimen deformation and failure process, which can be used as a precursor to deter- mine the coal specimen failure. AE information occurs in the interval of cyclic loading and unloading process, and the change trends of energy, count and amplitude are same and coincide with the stress of the coal specimens. Felicity effect in the cyclic loading and unloading process is obvious, and the Felicity ratio FR is much less than 1. That the FR value continuously decreases with the cyclic stress level increasing shows the advance feature of AE memory in the cyclic loading and unloading process. The memory effect of Kaiser effect is poor, and Kaiser effect as the coal body sta- bility index needs to be cautious.