Analysis of dynamic stress characteristics and surrounding rock structure in shallow-buried longwall mining face

The overlying structure formed after underground coal seam mining is the result of breaking and migration of overburden strata, which is essentially a manifestation of the redistribution of stress in the surrounding rock after coal mining. Taking the stress structure of surrounding rock in shallow-buried long wall working face as the research object, using numerical simulation and theoretical analysis methods, starting with the distribution of stress field in surrounding rock after coal seam mining, the formation and instability process of surrounding rock stress structure are studied, and the overburden is analyzed from the point of stress field distribution law.The research results show that high stress zone of ellipsoid-like shape can be formed in the surrounding rock stress field after mining in shallow working face. The stress-bearing structure continuously develops and changes with the advance of working face until all the bedrock breaks and loses instability.After initial instability and failure, the rear support points of the spatial stress-bearing structure will migrate onto compacted gangue in the gob and provided support for surrounding rock. The formation and instability of spatial stress bearing structure is a dynamic evolution progress affected by mining face. Based on this, a pressure-bearing arch mechanics model of the spatial stress structure along the direction of the working face is established, and its morphological parameter equation in the overburden and its limit state height and span are derived. The mechanical state at any position on the axis of the pressure-bearing arch is obtained from point of the trace line of ultimate bearing arch is on the connection line where the bending moment of each rock layer is zero. Combined with the practice of the characteristics of the periodical fracture of the basic roof and its bedrock after mining in shallow coal seams, it is believed that the development and change law of the pressure-bearing arch structure is consistent with the “cantilever beam-articulated rock beam” structure instability characteristics. The results provide reference for the study of roof structure and stability of shallow buried working face.