Fracture law of overburden during the mining of shallow-buried close-distance coal seam group in Shanbei mining area

Shallow-buried close-distance coal seam groups are widely distributed in China. During repeated mining, the overburden movement is complex and mine pressure behavior is intense. Revealing the overburden fracture law under such geological conditions is of great significance for improving roof control. Taking the No. 2 and No. 4 coal seams of Fengjiata Coal Mine as the research object, this study combined similar material simulation experiments with UDEC numerical simulation to analyze the characteristics of overburden movement, fracture development, and stress evolution. The results show that during mining of the No. 2 coal seam, the main roof exhibited periodic fracture characteristics, with a maximum caving height of 10.2 m. Mining of the No. 4 coal seam caused bending and rotational failure of the interlayer primary key stratum and induced bending fracture of a higher-level key stratum. Stress monitoring shows that the peak roof abutment pressure coefficient is generally greater than 2.0, the stress concentration factor can reach up to 2.47, and the influential range is 40–70 m. Overburden fracturing in shallow-buried close-distance coal seam groups is characterized by distinct initial weighting and periodic weighting, asymmetric subsidence, and sudden stress increases. Key stratum stability is the core factor controlling mine pressure behavior and ensuring safe mining.