Roof Movement and Instability Fracture Characteristics in Shallow-Buried Thin Coal Seam Conventional Mining Faces

Abstract

Abstract The variation in the width of the mining face significantly affects the stability of the face, leading to potential roof fracturing and collapse. Additionally, strong coal and rock pressure can manifest, severely impeding the safe production of coal mines. This study uses the 16705 conventional working faces of Jinda Coal Mine as its engineering background to investigate the characteristics of roof strata movement and instability under conditions of variable-width mining in shallow-buried thin coal seams. First, using the key strata theory, the study estimates the dynamic load of the roof strata. Next, a mechanical model analysis of the roof strata movement in the working face is presented. This analysis shows the impact of different dimensions of the overhanging plate structure and residual overhanging structures in the corner on roof movement and its associated fracture mechanics. The findings indicated that as the roof width increases, the maximum bending deformation, deformation moment, and deformation stress rise logarithmically. Similarly, with an increased overhanging span of the roof, these metrics increase exponentially. In addition, as the size of the residual overhanging structures in the corner grows, these parameters rise linearly. Finally, this study analyzes the effect of roof instability on overlying pressure and estimates both the initial fracture step length and cyclic movement fracture step length of the roof. These insights offer valuable scientific guidance and a theoretical foundation for analyzing the adaptability of load-bearing pillars pressure in thin coal seam mining faces, bearing significant relevance to safety production.