Numerical simulation of stress and permeability evolution in damaged coal

Mining disturbance is the underlying cause of dynamic disasters such as coal-rock deformation, gas outbursts, and roof water inrush. Mining disturbance leads to damage in coal-rock structures and closely relates to stope cracks' distribution characteristics. Therefore, it is crucial to investigate the coupling effects of the stress field, damage field, and seepage field of coal. Firstly, we established a mechanical model considering the coupling effect of damage and elastoplasticity, which aimed to describe the softening process of coal-rock mechanical parameters and the mutation law of the permeability coefficient in the damage process. Next, we developed a pore-fracture fractal model of damaged coal. It was used to elucidate the inherent relationship between damage and pore-fracture characteristics in the process of coal-rock crushing. We then proposed a quantitative evaluation method for determining the permeability characteristics of coal under the influence of mining disturbances. Finally, a numerical simulation of damaged coal ‘s mechanical behavior and seepage characteristics under stress-seepage coupling was conducted. The development model's effectiveness was verified through comparison with experimental results. In summary, our research offered a solid scientific foundation for quantitative evaluation and accurate prediction of the evolution law of coal-rock permeability characteristics under the influence of mining disturbance.