Study on Coal Fragmentation Induced by Instantaneously Depressurized Gas and Its Influence on Coal and Gas Outburst: A Case Study of Different Gas Types

Coal and gas outburst, as an extremely destructive underground disaster, poses serious threats to mine production safety and global energy supply. The mechanisms of this disaster, particularly how gas participates in and affects coal mass fragmentation, have not been fully revealed. To investigate this issue, this study simulated the coal-breaking process through instantaneously releasing high-pressure gas saturated in coal samples under gas–stress coupled conditions, employed image binarization method to quantitatively analyze the deformation and fragmentation characteristics of coal samples under different gas conditions, and conducted corroborative analysis from mechanical response and expansion energy perspectives. The results demonstrated that with the enhancement of gas adsorptive ability, gas desorption rate and amount accelerated, carried energy increased, and the long-term adsorption-induced degradation became more significant, resulting in greater extents of coal sample damage. Additionally, a rarely reported axial stress rebound phenomenon was observed, where axial stress underwent rapid decline followed by swift recovery to nearly initial levels within extremely short timeframes. This indicated that the instantaneously depressurized gas-induced coal fragmentation in coal seams level intensifies with the enhancement of adsorptive ability of different gases. The findings of this study may be helpful for understanding the gas participating in coal–rock damage during outburst occurrences, further ensuring mine safety production and global energy security.