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 a-coustic emission of coal was carried out,the fragments were screened and statistically analyzed. The strength,fractal di-mension 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 e-mission have a positive correlation change with the strength during the failure process. The fractal dimension is charac-terized 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 empiri-cal formula of the cumulative energy of acoustic emission with the fractal dimension was established. The research re-sults provide a guidance for the quantitative analysis of the relationship between acoustic emission and mechanical be-havior.