周期荷载作用下煤岩声发射特征的颗粒流模拟

为研究周期荷载应力水平对煤样声发射特征的影响,采用PFC数值软件开展了3种不同应力水平的等幅周期荷载数值模拟试验,分析了周期荷载应力水平对煤样破坏循环次数、声发射计数及损伤演化特征的影响。研究结果表明:周期荷载作用下,煤样破坏过程中的声发射活动呈现初始、相对平静和活跃三阶段演化规律,且在煤样破坏前的周期荷载卸载阶段及低应力水平阶段几乎没有声发射活动;周期荷载上限应力水平的微小提高会加快煤样的破坏过程。提出了声发射比率的概念,当声发射比率大于1时,表明煤样即将发生破坏。声发射比率可作为预测现场工程煤体失稳的重要指标。

Particle flow simulation of acoustic emission characteristics of coal sample subjected to cyclic loading

In order to study the influence of cyclic loading stress level on acoustic emission characteristics of coal specimen, the PFC numerical simulation tests of equal stress amplitude cyclic loading with three stress levels were carried out. The influence of cyclic loading stress level on the cycle number of failure, acoustic emission counts and damage evolution of coal specimen is analyzed. The test results show that the acoustic emission activities of coal specimen subjected to cyclic loading exhibit three phases: namely, initial, relatively quiet and active phases. There is almost no acoustic emission activities in the unloading phase or low stress phase of cyclic loading before coal specimen’s failure. A slight increase in the peak stress of cyclic loading will accelerate the failure process of coal specimen. The concept of AE ratio is proposed, when the AE ratio is more than 1, which indicates that the coal specimen is about to be destroyed. And the AE ratio can be used as an important index to predict the instability of in-situ coal masses.