Distribution and evolution characteristics of advanced abutment pressure in hard-roof working faces

With increasing mining depth and increasingly complex geological conditions, existing studies on the distribution of advanced abutment pressure in working faces are difficult to be fully applicable to hard-roof conditions. To further reveal the distribution and evolution characteristics of advanced abutment pressure in hard-roof working faces, taking the 8105 working face of Majiliang Coal Mine of Datong Coal Mine Group Co., Ltd. as the engineering background, theoretical analysis, numerical simulation, and field measurements were comprehensively adopted, and the influences of different working face advance distances, mining speeds, and mining thickness on the distribution of advanced abutment pressure were analyzed. The results showed that the advanced abutment pressure in hard-roof working faces exhibited obvious zoning characteristics, which were successively divided, from near to far from the working face, into a pressure relief zone, a stress concentration zone, a secondary pressure relief zone, and an in-situ stress zone. With the increase in working face advance distance, the cantilever length of the main roof increased, the peak value of advanced abutment pressure in the stress concentration zone increased, the valley value of advanced abutment pressure in the secondary pressure relief zone decreased, and the range of the secondary pressure relief zone expanded. When the main roof fractured, a roof "rebound–retraction" effect occurred, causing the peak value of advanced abutment pressure to decrease, the valley value to increase, and the range of the secondary pressure relief zone to shrink. Increasing the mining speed or the mining thickness both led to an increase in the peak value of advanced abutment pressure, an expansion of the secondary pressure relief zone, and an increase in the pressure relief magnitude, thereby making the zoning characteristics of advanced abutment pressure in the working face more pronounced.