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A new brittleness index for hard coal considering unsteady energy release at post-peak stage |
HAO Xianjie1,2,3,YUAN Liang4,5,GUO Yanding3,LI Yulin3,ZHAO YiXin3,WANG Xinzhong3,ZHU Guangpei3,LU Zhiguo3,REN Bo5 |
(1. State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology(Beijing),Beijing 100083,China;2. Research Center of Coal Resources Safe Mining and Clean Utilization,Liaoning Technical University,Fuxin,Liaoning 123000,China;3. School of Resource and Safety Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;4. Anhui University of Science and Technology,Huainan,Anhui 232000,China;5. State Coal Mining
National Engineering Technology Research Institute,Huainan,Anhui 232000,China) |
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Abstract The post peak stress-strain curves of coal are often presented curved and benched drop. The current brittleness index expressed by gradient drop of compressive stress-strain cannot distinguish the linear,curved and benched drop. A new index to characterize the brittleness of hard coal based on unsteady energy release is thus proposed to overcome the problem. The brittleness of coal is the parameter characterizing the speed of energy release under the action of minute external energy in the post-peak stage. The mechanical and geometrical models of brittleness index were established according to the energy accumulation in pre-peak stage and the energy release in post-peak stage,which were validated theoretically and experimentally subsequently. Finally,the classification of bursting liability of coal according this index is studied. The results indicated that,compared with other indexes,this index can consider the longer nonlinear elastic phase of the hard coal,the shorter plastic and post-peak benched drop characteristics and so on.
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