Experimental study on the effects of inert gases on methane explosion characteristics in a loose medium environment

Gas explosion accidents are one of the major disasters threatening mine safety. The goaf areas in coal mines consist of loose media composed of fragmented coal and rock. Their strong concealment and destructive potential make the prevention and control of gas explosion accidents particularly challenging. In this paper, controlled experiments on methane explosions in loose media were conducted to investigate the variation of explosion characteristics under different inert gas environments, and to discuss the coupling mechanism by which inert gases and loose media influence methane explosion reactions. The results indicate that as the gas concentration increases, both the peak explosion overpressure and the maximum pressure rise rate of methane explosions in loose media tend to decrease. At the same concentration, CO2 is more effective than N2 in suppressing methane explosions in loose media. The maximum difference between the suppression rates of explosion overpressure by CO2 and N2 is 25.36%, with a maximum difference of 9.89% observed in the loose media. When the porosities are 0.504 and 0.534, the combined suppression effect of inert gases and loose media on methane explosion characteristics is better than that of either factor alone. At a porosity of 0.602, the promoting effect of loose media on methane explosions becomes more pronounced; however, as the concentration of inert gases increases, this promoting effect is significantly weakened. Moreover, with increasing inert gas concentration, the KG value of methane explosions in loose media shows a decreasing trend. When the porosities are 0.504 and 0.534, the KG value in loose media is only 3.27%–29.71% of that in a cavity, while at a porosity of 0.602, the KG value increases significantly to approximately 105.65%–450.03% of that in a cavity. N2 at concentrations of 5% and 10% has little effect on the KG value, whereas both N2 and CO2 at a concentration of 15% exhibit good explosion suppression effects. This work provides a theoretical basis for the formulation of prevention and control measures for gas explosion accidents in coal mine goaf areas.