Failure analysis of coal pillars and gateroads in longwall faces under the mining-water invasion coupling effect

The failure and design of coal pillars have always been the focus of research in the field of mining engineering, and there are often many water resources in goafs with rich aquifers. Under the influence of mining and long-term water invasion, it is easy to cause gradual failure and instability to coal pillars. Based on this, this paper proposes a numerical simulation method for the coupling of engineering scale mining-water invasion and a quantitative index of the damage ratio of coal pillars. The numerical parameters are calibrated with measurement data from coal-pillar stress. In the simulation process, the evolution of the strength, damage ratio, water pressure, stress, strain, and other parameters in coal pillars under the effect of mining-water invasion is realized, and the progressive failure mechanisms of coal pillars under mining-water immersion are revealed. On this basis, the effects of goaf water-level height and coal-pillar width on coal pillar stability are quantitatively analyzed, and the critical goaf water-level height corresponding to different coal-pillar widths is obtained. Using the simulation results of this paper, the instability of a coal pillar in a coal mine is effectively solved, and the deformation of the coal pillar rib and roof of the tailgate is reduced by 39.6% and 30.8%, respectively, which ensures the safe production of the longwall face.