Research on filling, pressure relief, and rock burst prevention in horizontal sublevel fully mechanized top coal caving of near-vertical coal seam groups

Current rock burst prevention measures for near-vertical coal seam mining primarily include blasting, hydraulic fracturing, and the establishment of protective layers. These measures either damage interlayer rock pillars and roof/floor strata or prove inadequate in resolving stress concentration in interlayer rock pillars at large mining depths, often resulting in significant surface subsidence. Using the Wudong Coal Mine as the engineering context, this study proposed a filling technique for goafs in horizontal sublevel fully mechanized top coal caving of near-vertical coal seam groups. This technique was intended to support interlayer rock pillars and roof/floor strata, reducing stress concentration in the surrounding coal and rock masses of the mining segments. Three filling schemes were designed: Scheme 1 involved filling the goaf in the first mining segment with high-strength materials, with ordinary materials used in other segments; Scheme 2 involved filling the goaf in the first segment with high-strength materials, with alternating high-strength and ordinary materials in other segments; and Scheme 3 involved filling the goaf in each segment with high-strength materials. Numerical simulations were conducted to assess the pressure relief and rock burst prevention effectiveness of the three schemes. Results indicated that, compared to no filling, the maximum vertical stress in interlayer rock pillars decreased by 25.07%, 26.57%, and 29.23% under the three schemes, respectively, while the maximum horizontal stress in the coal body of the subsequent segment decreased by 10.63%, 10.79%, and 12.34%, respectively. Considering both pressure relief effectiveness and economic feasibility, Scheme 3 with interval filling was identified as the optimal solution. It was suggested that this approach be combined with real-time intelligent monitoring technology in high-stress areas to promptly support interlayer rock pillars, thus reducing stress concentration and preventing rock bursts.