Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal.To study the crushing effect and its evolution during out...Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal.To study the crushing effect and its evolution during outbursts,coal samples with different initial particle sizes were evaluated using a coal and gas outburst testing device.Three basic particle sizes,5–10 mesh,10–40 mesh,and 40–80 mesh,as well as some mixed particle size coal samples were used in tests.The coal particles were pre-compacted at a pressure of 4 MPa before the tests.The vertical ground stress(4 MPa)and the horizontal ground stress(2.4 MPa)were initially simulated by the hydraulic system and maintained throughout.During the tests,the samples were first placed in a vacuum for 3 h,and the coal was filled with gas(CH4)for an adsorption time of approximately 5 h.Finally,the gas valve was shut off and the coal and gas outburst was induced by quickly opening the outburst hole.The coal particles that were thrown out by the outburst test device were collected and screened based on the particle size.The results show the following.(1)Smaller particle sizes have a worse crushing effect than larger sizes.Furthermore,the well-graded coal particles are weakly broken during the outburst process.(2)As the number of repeated tests increases,the relative breakage index grows;however,the increment of growth decreases after each test,showing that further fragmentation becomes increasingly difficult.展开更多
基金This research was financially supported by the National Natural Science Foundation of China(No.51434003)the Project of the Ministry of Emergency Management of the People's Republic of China(sichuan-0011-2018AQ)the Department of Science and Technology of Sichuan Province(19YYJC2854).
文摘Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal.To study the crushing effect and its evolution during outbursts,coal samples with different initial particle sizes were evaluated using a coal and gas outburst testing device.Three basic particle sizes,5–10 mesh,10–40 mesh,and 40–80 mesh,as well as some mixed particle size coal samples were used in tests.The coal particles were pre-compacted at a pressure of 4 MPa before the tests.The vertical ground stress(4 MPa)and the horizontal ground stress(2.4 MPa)were initially simulated by the hydraulic system and maintained throughout.During the tests,the samples were first placed in a vacuum for 3 h,and the coal was filled with gas(CH4)for an adsorption time of approximately 5 h.Finally,the gas valve was shut off and the coal and gas outburst was induced by quickly opening the outburst hole.The coal particles that were thrown out by the outburst test device were collected and screened based on the particle size.The results show the following.(1)Smaller particle sizes have a worse crushing effect than larger sizes.Furthermore,the well-graded coal particles are weakly broken during the outburst process.(2)As the number of repeated tests increases,the relative breakage index grows;however,the increment of growth decreases after each test,showing that further fragmentation becomes increasingly difficult.
