煤岩蠕变声发射特征试验研究

Acoustic Emission Characteristics of Coal Creep under Step Load

利用MTS815岩石伺服试验系统和AE21C声发射监测系统对煤岩进行了分级加载声发射试验.试验结果分析表明,煤岩分级加载过程存在蠕变应力阈值,在达到该阈值之前,各个应力水平上的煤岩变形很不明显,当加载水平大于该阈值时才发生明显蠕变变形.在瞬态蠕变阶段,煤岩内微孔隙、裂隙逐渐扩展,声发射活动逐渐增强;在稳定蠕变阶段煤岩蠕变变形速率趋于平稳,新生裂隙较少,声发射事件少且能量低;在加速蠕变阶段煤体内产生大量裂隙并逐渐发育至宏观破裂失稳,储存的能量在较短的时间内快速释放,声发射事件数及能量均达到最大值.煤岩的声发射特征较好地反映了其蠕变过程中的损伤演化过程.

Experiments on acoustic emission （AE）characteristics of coal specimens under step load were carried out with MTS815 servo-controlled rock mechanical test system and AE21C detection system. Analysis of the experimental results showed that the step load had a creep stress threshold, creep deformation was not obvious until the loading exceeds the threshold. During the transient creep stage, AE activities gradually increased with the expending of the micro-pores and micro-fractures inside coal. During the steady creep stage, the creep deformation rate tended to be stabilized and the new fractures were less, and the AE events were less and their energy was low. During the accelerated creep stage, a large number of new fractures occur and quickly develop and cause the coal specimen to the macro fracture failure, the stored energy quickly released in a short period of time. Simultaneously, the AE events and their energy reached to the maximum value. The creep damage evolution process of coal can be well reflected by AE characteristics.