Study on Strata Behavior in Upward and Downward Slicing Backfill Mining of Ultra-Thick Coal Seams

Baijigou Mine, facing resource depletion, must recover safety pillars beneath the riverbed. To control surface subsidence, layered paste backfill lane by lane was adopted. Using FLAC^3D numerical simulation, this study analyzes strata behavior in upward and downward slicing backfill mining of an ultra-thick coal seam. Optimizing crosscut spacing identified the two-lane interval scheme as optimal. Results show upward slicing better controls roof subsidence and stress distribution, forming a step-like support structure that effectively restrains overburden deformation. Downward slicing exhibits poorer stability due to unrecovered early roof pressure relief.