MAIN ROOF MECHANICAL MODEL AND NUMERICAL SIMULATION OF COMPOSITED BACKFILLING LONG-WALL FACE IN STEEPLY DIPPING COAL SEAM

The overlying strata movement of steeply dipping coal seam is complicated with large deformation and fracturing of the roof, which often requires the composited backfill mining to effectively improve the stability of surrounding rock. In this paper, the 3221 working face of a test coal mine was taken as the engineering research background. Based on the analysis of the main roof mechanics model of the composited backfilling long-wall face in the steeply dipping coal seam, the finite-difference program FLAC3D and MATLAB were used to numerically study the stress and displacement fields of the main roof under different coal seam dip angles and amounts of artificial waste rock filling. The results showed that as the dip angle increased, the normal force component decreased whereas the tangential force component and the horizontal stress of the roof beam increased. The horizontal displacement increased before the vertical displacement decreased, and the degree of deformation decreased with the increase of the dip angle. The overhanging area of the roof beam reduced with the increase of the filling amount of artificial waste rock, which led to a decreased deformation degree of the roof beam, and the influence on the main roof movement was more obvious than the change of dip angle. The numerical simulation results were found consistent with those from the mechanical model, which proved the rationality of the mechanical model. In general, this research can provide a theoretical basis for the safe and efficient production of the composited backfill mining in steeply dipping coal seams.