Numerical simulation of damage evolution in coal under stress–seepage–adsorption coupling conditions

Deep coal mining increasingly encounters complex geological conditions characterized by high ground stress, elevated gas pressure, and intensive mining activities. These factors interact through multi-field coupling mechanisms, intensifying dynamic disasters such as gas outbursts. To investigate the damage evolution of coal under such coupled conditions, this work develops an integrated numerical simulation framework. The approach incorporates three major components: (i) the Weibull statistical distribution to describe the heterogeneous mechanical properties of coal, (ii) the Mohr-Coulomb shear failure criterion and maximum tensile stress criterion to evaluate damage initiation and propagation, and (iii) coupled control equations for deformation mechanics, gas seepage, and adsorption-induced strain. The role of confining pressure on coal’s mechanical behavior is examined through uniaxial and biaxial compression tests, and the patterns of damage evolution under stress–seepage–adsorption coupling conditions are systematically analyzed. The results indicate that increasing confining pressure elevated peak stress and strain while inhibiting damage progression. In contrast, higher gas pressure differences accelerate coal failure, with coal showing greater sensitivity to changes in confining pressure. Moreover, unidirectional gas flow produces a decreasing stress and damage distribution along the flow direction, whereas bidirectional gas flow generates distinct damage patterns due to differing boundary conditions. This work provides new insights into the mechanisms of coal damage under multi-field coupling conditions, offering theoretical support for predicting and mitigating dynamic disasters in deep coal mining.