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| Testing of fragments ejection characteristics and burst kinetic energy index for different types of coal and rock |
| ZHAO Tongbin1，2，GUO Lei1，2，YIN Yanchun1，2，XIAO Yaxun3，LI Shihang1，2，GAO Zitong1，2 |
| (1. College of Energy and Mining Engineering，Shandong University of Science and Technology，Qingdao，Shandong 266590，China；2. Shandong Key Laboratory of Intelligent Prevention and Control of Dynamic Disaster in Deep Mines，Shandong University of Science and Technology，Qingdao，Shandong 266590，China；3. State Key Laboratory of Geomechanics and Geotechnical Engineering Safety，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China) |
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Abstract During dynamic failure of coal and rock，a large number of fragments are ejected，and the ejection distance and kinetic energy of these fragments can more intuitively reflect the intensity of the specimen?s failure. This paper proposes a test method for measuring the ejection kinetic energy of coal and rock fragments，and the feasibility of the method is verified through numerical simulation examples. Experimental research is conducted on the fragments ejection characteristics of different types of rocks. Based on this，a classification method for burst liability is proposed based on the burst kinetic energy index. Furthermore，the influence of loading stiffness on the fragments ejection characteristics and burst kinetic energy index of coal is analyzed. The results show that the fragments ejection characteristics of coal and rock specimens vary significantly among different lithologies. The fragments ejection mass proportion and ejection distance of granite and basalt are notably greater than those of sandstone，marble，and coal with lower strength. The stronger the burst liability of the specimen，the greater the fragments ejection distance and kinetic energy. The ejection kinetic energy of the fragments has a positive power function relationship with the uniaxial compressive strength，and a positive linear relationship with both the burst energy index and the residual elastic energy index. The recommended ranges for the burst kinetic energy index for coal with no burst liability，weak burst liability，and strong burst liability are ＜30 J/m³，30～300 J/m³，and＞300 J/m³，respectively. As the stiffness ratio of the testing machine to the specimen decreases，the energy supplied by the testing machine to the coal specimen increases，resulting in an increase in the fragments ejection distance and kinetic energy of the specimen after failure. The burst kinetic energy index has a positive power function relationship with the stiffness ratio. The proposed test method for measuring the specimen fragments ejection kinetic energy and the burst kinetic energy index can effectively evaluate the burst liability and damage intensity of coal specimens.
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