Disaster-causing mechanism and control technology of interlayer rock breakage in gently inclined close distance coal seams mining

Abstract Aiming at the complex issue of dynamic disasters induced by hard rock layers fracture during the mining of gently inclined close distance coal seams, this study employs an integrated approach combining numerical simulation, microseismic monitoring, and mechanical analysis to investigate the fracture evolution process of hard rock layers under the influence of an inverted trapezoidal overburden. A cantilever beam structural model of interlayer rock layers was established, from which the deflection curve and rotation angle equation at the critical fracture state were derived. The elastic energy released upon fracture of the cantilever beam was quantified. Furthermore, by considering the characteristics of the overburden above residual coal pillars, the interplay among the total energy released during interlayer rock fracture, the strength of the cantilever structure, and the inverted trapezoidal overburden load was elucidated. Specifically, a heavier inverted trapezoidal load increases the disaster-induced energy applied to the cantilever structure, a longer cantilever beam accumulates greater elastic energy, and a stiffer beam structure can accumulate more energy. The interaction between these three factors makes it easy to induce strong mining pressure when the hard rock layers break during close distance coal seam mining. Accordingly, combined prevention measures involving water injection softening and blasting roof cutting were proposed to mitigate dynamic hazards and ensure safe mine production.