The shaped blasting experimental study on damage and crack evolution of high stress coal seam |
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| Institution: | 1. School of Safety Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu, China;2. Key Laboratory of Mine Safety and High Efficient Mining Jointly Built by Province and Education Ministry, Anhui University of Science and Technology, Huainan, Anhui 232001, China;3. College of Safety Science and Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001, China;1. Xi''an University of Science and Technology, Xi''an, 710054, Shaanxi, China;2. Xi''an Key Laboratory of Urban Public Safety and Fire Rescue, Xi''an, 710054, Shaanxi, China;1. School of Chemical Engineering, Anhui University of Science and Technology (AUST), 168, Taifeng St., Anhui, 232001, China;2. Department of Chemical and Materials Engineering, National Yunlin University of Science and Technology (YunTech), 123, University Rd. Sec. 3, Douliou, 64002, Yunlin, Taiwan;3. Department of Occupational Safety and Health, Jen-Teh Junior College of Medicine, Nursing and Management, 1, Jen-Teh Rd., Houlong, Miaoli, 35665, Taiwan, ROC;1. College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, 454003, Henan, PR China;2. State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization, Jiaozuo, 454003, Henan, PR China;3. State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Jiaozuo, 454003, Henan, PR China;1. College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580, China;2. Saifeite Engineering Group Co. Ltd., Qingdao, 266061, China;3. Department of Safety, Health, And Environmental Engineering, National Yunlin University of Science and Technology, Yunlin, 64002, Taiwan, ROC |
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| Abstract: | In the deep high stress coal and rock mass, the efficiency of the ordinary blasting method is constantly affected by the high pressure. This study investigates the shaped blasting technology with increased blasting efficiency, develops a mechanical model for coal crack expansion during shaped blasting, and examines the force-energy action of energy-gathering jets during coal splitting. The established model was combined with experiments and simulations to reveal the damage and evolution of cracks in coal and rock masses. Experiments demonstrate that shaped blasting can create an energy-gathering jet that causes a directional fracture in the test block. The peak of compressive strain in the energy-gathering direction is 1.12 times greater than that of ordinary blasting, and the static action period of the explosive gas is prolonged by 1.3 μs according to the stress curve. Moreover, the peak pressure strain increased 3.2 times, and the pull strain peak increased 3.92 times. The damage amount was represented by the resistivity and ultrasonic wave speed, and shaped blasting causes 1.2 and 1.5 times greater damage than ordinary blasting. The research results provide technical methods for safe and rapid penetration blasting in deep high-ground stressed coal mines. |
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| Keywords: | High-ground stress Rock mechanics Energy-gathering direction Damage characteristics Pressure strain |
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