Coal and gas outburst remains a critical and persistent challenge in coal extraction, posing a profound threat for mine safety. The underlying mechanisms of such disaster, particularly the gas-driven coal fragmentation, continue to elude comprehensive understanding. To explore this problem, in this paper, gas seepage regularity in different structural bituminous coal and its influence on outburst-coal breaking were investigated through strength tests, isothermal adsorption tests, and gas seepage tests of stressed coal under various conditions. The results indicated that coal permeability decreased as axial stress, confining pressure, and gas kinetic diameter increased. That meant outburst-induced abrupt stress unloading and coal matrix destabilization changed gas seepage characteristics. As a result, a self-reinforcing cycle effect where outburst-coal breaking and gas seepage are mutually stimulated was formed in a short time period when outbursts initiated, which further promoted outburst-coal breaking and outburst initiation. The findings of this study enhance our understanding of the mechanism of gas participating in coal fragmentation during outbursts, which are significantly conducive to gas disaster prevention, sustainable coal production, and efficient CBM development, further ensuring global energy security.

Acid treatment has been proven to effectively reduce reservoir fracture pressure, but the variation pattern of sandstone brittleness after acid treatment remains unclear. To effectively evaluate the characteristics of brittleness changes, uniaxial compression tests were conducted on tight sandstone subjected to acid treatment for different durations, and a brittleness index evaluation method based on radial strain response was established. The results show that sandstone uniaxial compressive strength decreases stepwise with prolonged acid treatment. Elastic modulus decreases slowly initially, drops sharply after 24 h of acid treatment, and stabilizes between 120 and 168 h. Poisson’s ratio decreases linearly after 6 h of acid treatment. The brittleness index first increases and then decreases, peaking at 12–24 h of acid treatment—consistent with AE results showing more high-intensity signals during the elastic compression stage of axial stress-strain curves. After acid treatment, sandstone crack initiation stress first increases slowly, then gradually decreases, and finally drops rapidly. This is attributed to acid-rock reaction-induced dissolution of minerals and cementing materials, which detaches fine-grained matrix particles, increases porosity, and reduces crack initiation stress. The findings provide a reference for engineering design and construction of high fracture pressure tight sandstone reservoirs.