Local seismicity induced unstable crack propagation in a coal and its effect on coal burst characteristics

Minghe JU; Han ZHU; Linming DOU; Lihua HU; Zepeng HAN; Xiaotao MA

doi:10.13225/j.cnki.jccs.2023.0139

Meitan xuebao (May 2023)

Local seismicity induced unstable crack propagation in a coal and its effect on coal burst characteristics

Minghe JU,
Han ZHU,
Linming DOU,
Lihua HU,
Zepeng HAN,
Xiaotao MA

Affiliations

Minghe JU: State Key Laboratory of Intelligent Construction and Healthy Operation & Maintenance of Deep Underground Engineering, China University of Mining and Technology, Xuzhou　221116, China
Han ZHU: State Key Laboratory of Intelligent Construction and Healthy Operation & Maintenance of Deep Underground Engineering, China University of Mining and Technology, Xuzhou　221116, China
Linming DOU: State Key Laboratory of Coal Exploration and Intelligent Mining, China University of Mining and Technology, Xuzhou　221116, China
Lihua HU: State Key Laboratory of Intelligent Construction and Healthy Operation & Maintenance of Deep Underground Engineering, China University of Mining and Technology, Xuzhou　221116, China
Zepeng HAN: State Key Laboratory of Coal Exploration and Intelligent Mining, China University of Mining and Technology, Xuzhou　221116, China
Xiaotao MA: State Key Laboratory of Coal Exploration and Intelligent Mining, China University of Mining and Technology, Xuzhou　221116, China

DOI: https://doi.org/10.13225/j.cnki.jccs.2023.0139
Journal volume & issue: Vol. 48, no. 5
pp. 2035 – 2048

Abstract

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In this study, the acoustic emission evolution and stress drop processes of brittle coal specimens under quasi-static compression were investigated by experiments and numerical simulations, to reveal the pattern of mesoscopic crack evolution and its effect on the macroscopic coal burst characteristics. The results indicate that the crack evolution law during an instantaneous stress drop is dramatically different from that under quasi-static compression, in terms of both the inducement mechanism and the pattern and scope of crack propagation. Upon an instantaneous stress drop, mesoscopic tensile cracks around the free face rapidly propagate and coalesce. Subsequently, massive debris are formed and ejected, due to slippage-triggered high-energy seismicity events. During the process, tensile cracks are dominant while shear cracks are mainly generated during crack coalescence. In addition, high-energy seismicity events are localized and then extend peripherally, where the dynamic disturbance leads to rapid evolution of local mesoscopic cracks and structural instability. As a result, stress drop and coal burst take place at the macroscopic scale. Generally, temporality among seismicity, stress drop and coal burst was found. Moreover, coal burst intensity is correlated with the stiffness ratio and released energy of a stress drop event. The critical stiffness ratio is 18.2 for coal specimens in this study, below which no coal burst occurs. With the increase of stiffness ratio and energy release, four types of coal burst behavior, i.e. slight debris ejection, massive debris ejection, block ejection, and coal bump, successively take place. The mean ejection velocity and kinetic energy of debris, as well as the maximum debris ejection velocity, generally increase with the rise of stiffness ratio. Conclusions and findings in this paper are beneficial to the understanding of coal burst mechanism under quasi-static compression.

Published in Meitan xuebao

ISSN: 0253-9993 (Print)
Publisher: Editorial Office of Journal of China Coal Society
Country of publisher: China
LCC subjects: Science: Geology; Technology: Mining engineering. Metallurgy
Website: http://www.mtxb.com.cn/indexen.htm

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