Occurrence of coal–gas disasters: A combined criterion considering temperature effect

Coal–gas compound disasters (herein referred to as compound disasters) pose a significant dynamic geological threat in deep coal mine roadways. However, the occurrence conditions and mechanisms of these events remain insufficiently understood due to the intricate coexistence modes of tensile and shear failure in the surrounding rocks of roadways, which are caused by the deep storage environment characterized by high in situ stress, gas pressure, and temperature. Based on the shear and tensile failure of gassy coal–rock materials, this study develops a “stress–gas–temperature” roadway mechanical model for compound disasters in gassy coal seams. The critical indices for these disasters are derived, including a crucial softening zone radius and critical stress. Compound disasters occur within a threshold range determined based on the critical indices from shear-only and tensile-only damage assumptions, and confirmed via quantitative calculations from several case studies. These critical indices are mainly controlled by uniaxial tensile/compressive strength, brittleness index, support stress, gas pressure, and temperature variations. Accordingly, field guidance for monitoring and early warning of compound disasters is proposed. Finally, the occurrence mechanisms of compound disasters are elucidated from the perspective of the tensile and shear failure coexistence modes in gassy coal–rock materials. This study supports quantitative identification and forecasting of potential compound disasters in engineering geology.