Experimental study on precursor characteristics of coal and gas outbursts based on acoustic emission energy analysis

Coal and gas outbursts are the most serious dynamic disasters in the process of coal mining, and unclear understanding of outburst mechanisms restricts the reliability and effectiveness of disaster early warning. Taking Sunjiawan outburst coal seam in Fuxin as the research object, the similarity experiments of coal and gas outburst with different mining depths were carried out using a self-developed true triaxial test device of coal and gas outburst and the DS5 series full-information acoustic emission signal analysis and testing system. The energy evolution process of coal and gas outburst was analyzed, and the relationship between acoustic emission parameter characteristics and precursor information of coal and gas outburst was established. The results show that the coal and gas outburst process has four stages including early incubation, late incubation, excitation-development and termination and in the process, the acoustic emission energy signals show steady-rise-peak variation, indicating that coal and gas outburst is a mechanical process of coal damage and energy accumulation. In the early stage of gestation, the AE energy is at a low level with a steadily rising accumulation, the low energy frequency dominates, and the outburst danger is weak. In the late stage of gestation, the AE energy increases greatly and high-energy frequency dominates, highlighting the risk. The difference of AE energy signals in different periods of outburst can be used as outburst precursor information to monitor the dynamic changes of coal and rock internal fractures in real time and further to guide outburst prediction and early warning. Based on acoustic emission energy, a quantitative index reflecting the danger level of coal and gas outburst in incubation period is defined, which provides scientific reference for the prediction and early warning of dynamic disasters in coal mining. © 2021, Science Press. All right reserved.