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Catastrophic events in underground coal mining usually originate from weak structures such as bedding and fractures. This study investigated the failure characteristics of coal samples with different bedding orientations by employing acoustic emission (AE) technology. Analysis of the AE time series, including ringing counts, amplitude, b-value, and the AF-RA relationship, was performed to characterize the failure behavior of the bedded coal. The synergistic effect of bedding and in-situ stress on the failure mechanism was also examined. The anisotropy of strain energy during the deformation and failure process was analyzed. The results indicate that bedding significantly influences the AE activity of coal during the failure process. Before failure, various AE parameters exhibit distinct precursory signals. Specifically, the sensitivity is found to be: b-value > cumulative ringing counts > amplitude > ringing counts. With increasing bedding orientation, the proportion of tensile cracks decreases initially, reaching a minimum at 60°. Conversely, the proportion of shear cracks exhibits an opposite trend. Microcrack development within the coal samples is primarily concentrated in the unstable crack extension and post-peak failure stage. The total strain energy, elastic strain energy, and dissipated energy display of coal sample show a V-shaped variation trend and reach their minimum values when bedding orientation is 60°. The degree of anisotropy for total strain energy, elastic strain energy, and dissipated energy exhibited a tendency to increase initially and then decrease with increasing stress.The research results can provide a scientific theoretical foundation for the stability assessment and prediction of underground mining engineering.
Guo-ning et al. (Sat,) studied this question.