Surface Water Resource Protection in a Mining Process under Varying Strata Thickness—A Case Study of Buliangou Coal Mine, China

The mining of shallow buried and thick coal seams may cause ground settlement, loss of surface water, and even soil desertification in arid–semi-arid climate zones. The key to protecting surface water resources through the technology of separated strata grouting is to study the evolution of the separation space under the key stratum (KS) with the change of strata. Aiming at the section of underground strata characteristics of F6202 and F6208 working faces, similar simulation tests under three typical geological conditions were carried out. Based on the experimental results, a theoretical calculation model was established, and the practice of separation grouting was carried out. The results show that, under the conditions of a thick coal seam with one KS, the structure formed by breaking strata below the KS was relatively unstable, and the separation space was relatively large, which is likely to cause serious ground settlement. More seriously, with the increase of the weakly consolidated layer and coal seam thickness, the increase of the ratio of rock to soil in the weakly consolidated layer, and the decrease of the thickness of the strata below the KS (two KS condition), the separation space was further increased. Based on the above analysis, combined with the real-time feedback data of the grout amount and pressure on hydraulic support, the position of the grouting borehole was determined, and the speed of mining advance was adjusted in time, thus effectively controlling the curvature of the ground settlement, protecting the integrity of the red clay layer near the surface, and consequently protecting water resources