Open AccessArticle

# Study on the Evolution Law of Overburden Breaking Angle under Repeated Mining and the Application of Roof Pressure Relief

by Feng Cui 1,2,3,*, Tinghui Zhang 1,2, Xingping Lai 1,2, Jiantao Cao 1,2 and Pengfei Shan 1,2
1
Energy School, Xiâ€™an University of Science and Technology, Xiâ€™an 710054, China
2
Key Laboratory of Western Mines and Hazard Prevention of China Ministry of Education, Xiâ€™an University of Science and Technology, Xiâ€™an 710054, China
3
Key Laboratory of Coal Resource Exploration and Comprehensive Utilization, Ministry of Land and Resources, Xiâ€™an 710021, China
*
Author to whom correspondence should be addressed.
Energies 2019, 12(23), 4513; https://doi.org/10.3390/en12234513
Received: 21 October 2019 / Revised: 22 November 2019 / Accepted: 25 November 2019 / Published: 27 November 2019
Aiming at the serious problems caused by coal mine mining activities causing the rock burst accidents, this paper is based on rock mechanics and material mechanics to establish the key layer breaking by the double-key layer beam breaking structural mechanics model of a single working face and double working face under repeated mining. The theoretical calculation formula of the angle was used as the theoretical basis for the elevation angle of the pre-reloading hole of the hard roof. The rationality and reliability of the formula were verified by the physical similarity simulation experiment and the 3 Dimension Distinct Element Code numerical simulation experiment, revealing the rock formation under the influence of repeated mining. The results show that the derived key layer breaking angle formula is suitable for the theoretical calculation of the breaking angle of the key layer of a single coal seam when the repeated disturbance coefficient is λ = 1; when it is λ = 2, it is suitable for the repeated mining of the short-distance double-coal mining. The rationality and reliability of the theoretical formula of the breaking angle of the double key layer of single coal seam and double coal seam were verified by the physical similarity simulation experiment. Through the 3DEC numerical simulation results and theoretical calculation results, the W1123 working face hard top pre-cracking pressure relief drilling elevation angle was 78°. The drilling peeping method was used to verify the results. The results show that the theoretical formula of the critical layer breaking angle is well applied in engineering practice. View Full-Text
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MDPI and ACS Style

Cui, F.; Zhang, T.; Lai, X.; Cao, J.; Shan, P. Study on the Evolution Law of Overburden Breaking Angle under Repeated Mining and the Application of Roof Pressure Relief. Energies 2019, 12, 4513.