Research on the fracture evolution law and combined bearing structure load of shallow buried coal seam group

The high-intensity mining of shallow-buried coal seams leads to the fracture of the bearing strata to form a combined bearing structure, which complicates the distribution of cracks in the overlying rock and causes serious damage to the surface. In order to study the relationship between the evolution law of the overburden fissures and the bearing structure of the bearing rock in the mining of the shallow coal seam group, and the working resistance value of the support to keep the bearing rock stable, the coal mining of Hanjiawan Coal Mine 2⁻² and 3⁻¹ in the Shenfu mining area in northern Shaanxi was studied. In the background, through field observation and similar simulation experiments, the evolution law of coal seam group mining cracks, the combined bearing structure of bearing rock layers and the relationship between the two were obtained. The mechanical model of combined bearing structure was established by theoretical calculation method, and the support work of the combined bearing rock layer to maintain stability was studied. resistance. The research shows that the evolution process of overlying fissures in coal seam mining can be divided into four stages: the upper coal seam mining rapid growth stage, the upper coal seam mining steady growth stage, the lower coal seam mining rapid growth stage, and the lower coal seam mining stable growth stage. This leads to different fissure evolution forms and subsidence characteristics on the surface. The surface of the “step rock beam” structure subsides in steps, and the surface of the “hinge rock beam” structure subsides continuously; The fractured structure of the bearing rock formation in the lower coal seam is obtained from the filling rate and mining height of the interlayer, and it is revealed that the fractured combined structure of the bearing rock formation in the shallow buried coal seam mining group is “step-hinged” structure, “hinged-hinged” structure, “hinged-hinged” structure. The combined form of the “step” structure and the “step-step” structure. Based on the fractured composite structure of the bearing rock, the mechanical model of the bearing rock bearing structure of the shallow buried coal seam group mining is established, and the calculation method of the working resistance of the bearing rock to maintain the stability of the support is obtained, and the field measurement results are verified.