瓦斯压力作用下煤岩的声发射非线性演化特征

Nonlinear evolution characteristics of acoustic emission and fracture mechanism of coal under gas pressure

研究含瓦斯煤岩的声发射演化特征对于揭示煤岩的变形破坏机制有着重要作用。利用渗流-应力耦合试验系统进行了含瓦斯煤岩三轴压缩试验,研究了瓦斯压力对声发射非线性演化特征的影响,并基于强度理论分析了瓦斯压力对煤岩强度的影响机制。结果表明:煤岩的声发射能量和体应变演化有较好的对应关系。随着瓦斯压力的减小,声发射能量快速增加阶段曲线变得更加陡峭,也表明煤岩的脆性破坏特性加强。声发射分形数呈现在峰值段之前下降,峰后又增长的趋势。峰前阶段,分维的降低表明煤岩内部微破裂的增多和主破裂的出现,煤岩内部损伤由无序随机分布逐渐向宏观有序破坏过渡。

The study on the evolution characteristics of acoustic emission of coal containing gas plays an important role in revealing the deformation and failure mechanism of coal.The triaxial compression tests on the coal containing gas is carried out by using the seepage stress coupling test system.The influence of gas pressure on the nonlinear evolution characteristics of acoustic emission of coal are studied,and the influence mechanism of gas pressure on coal strength is analyzed based on the strength theory.The results show that there is a good corresponding relationship between the acoustic emission energy and the volume strain evolution of coal.With the decrease of gas pressure,the acoustic emission energy increases rapidly,and the stage curve becomes more steep,which also indicates that the brittle failure characteristics of coal are strengthened.The fractal number of acoustic emission decreases before the peak and increases after the peak.At the pre-peak stage,the decrease of fractal dimension indicates the increase of micro-fracture and the appearance of main fracture in coal,and the internal damage of coal gradually transits from disordered random distribution to macro-ordered failure.