Experimental analysis of the intensity and evolution of coal and gas outbursts

•The energy difference provided by in situ stress and gas pressure is hundred times.•The temperature exerts little influence on the outburst intensity.•The potential amount of coal ejected can be predicted by the IEERG.•The whole outburst process can be divided into four main phases. Coal and gas outburst (hereinafter referred to as “outburst”) is a complicated dynamic disaster formed in the temporal and spatial evolution process. To further improve our understanding of outburst mechanism and help more effective outburst prevention and control measures to be devised, a finite number of outburst simulation tests were carried out in the study. The results show that the contribution of the gas pressure to the energy required for an outburst is hundreds of times that of the in situ stress during the outburst. With increasing mining depths, the higher the in situ stress, the gas pressure, and the temperature; however, the temperature shows the lowest influence on the outburst intensity among various parameters such as gas pressure, the thickness of soft coal, and the temperature. The initial expansion energy of releasing gas (IEERG) is an index reflecting the influences of in situ stress, gas pressure, and coal strength on outburst intensity. The test results indicate that the potential amount of coal ejected can be predicted by measuring the IEERG of coal masses and the thickness of soft coal in outburst-prone zones. According to the failure characteristics of coal masses after an outburst, the larger the outburst intensity is, the smaller the volume of residual coal area relative to the outburst holes. The shapes of extrusive coal-gas flows after an outburst show that the outburst process is a chain of events occurring over multiple cycles as follows: preparation, initiation, development, and termination. The recorded video footage of an outburst also shows this.