煤体破裂分形特征与声发射规律研究

探究离散性影响下煤体力学行为演化机制及失稳预测方法是有效提高冲击地压预测准确性的关键，开展煤受载破坏声发射监测试验并对破碎块体筛分统计，获得了强度、块体分形特征、声发射信号规律及其相互关系。研究结果表明:受裂隙及夹矸等影响煤体内部形成承载结构缺陷区导致其强度具有显著离散性，含有夹矸或裂隙越多，煤体受载过程弹性区越短承载能力越低，破碎后完整性较高，峰后软化特征明显，煤体单轴压缩破坏块度分形维数为2.08~2.60略高于岩石，碎块分形维数随峰值应力增加而升高，将质量频率分布曲线的斜率定义为碎块密集度(k)，碎块密集度越小煤体分形维数越大，破碎块体的数目越多体积越小破碎程度越高;煤体受载过程声发射能量、信号密集度和能量累积量随强度正相关变化，声发射累积量正比于分形维数，结合试验统计结果，深入分析了声发射能量与分形维数间的内在联系，并建立了声发射累积总能量随分形维数变化的经验公式，研究成果为定量的分析声发射信号与煤体力学行为间相互关系提供指导。

Investigate on the fractal characteristics and acoustic emission of coal fracture

To investigate the evolution mechanics of mechanical behavior and the instability prediction method of coal is the key to improve the predictive accuracy of rockburst.In this study,the experiment of mechanical properties and acoustic emission of coal was carried out,the fragments were screened and statistically analyzed.The strength,fractal dimension and acoustic emission of coal and the interrelationships among them were obtained.The results show that there are some bearing structure defect areas inside the coal which are effected by crack and gauge.The more the initial damage in it,the lower the bearing capacity,and the higher damage integrity.The softening characteristics after the peak are more obvious.The fractal dimension of coal is in the range of 2.08-2.60 which is slightly higher than that of rock and it increases with the peak stress improvement.The slope of the mass frequency distribution curve is defined as the block density (k),the smaller of it the more fractal dimension,the larger the number of broken blocks,the smaller the volume,the higher the degree of fragmentation.The energy,signal density and energy accumulation of acoustic emission have a positive correlation change with the strength during the failure process.The fractal dimension is characterized as the degree of fragmentation.The energy accumulation of acoustic emission is proportional to peak strength and fractal dimension.The relationship between acoustic emission and fractal dimension was analyzed,and an empirical formula of the cumulative energy of acoustic emission with the fractal dimension was established.The research results provide a guidance for the quantitative analysis of the relationship between acoustic emission and mechanical behavior.