Time-dependent ground stability of inclined backfilled stope characterized by creep behavior

Backfill has been routinely adopted in underground mines as ground support measure. However, the ground stability enhancement by backfill received limited research attention probably due to the conventional assumption that fill material exhibits significantly lower stiffness than host rocks. Notably, recent pioneering work revealed time-dependent ground stability around backfilled stope with vertical walls through numerical modelling. In practice, underground stopes typically exhibit more or less degree of inclination, which alters the stress state in peripheral rocks and may induce serious instability and dilution, particularly in stope hanging wall. It is thus imperative to analyze the time-dependent ground stability of inclined backfilled stopes for backfill structure design. Therefore, comprehensive numerical simulations were performed with FLAC3D to address this knowledge gap by incorporating coupled analysis of backfill consolidation behavior and the long-term creep deformation in surrounding rocks. The ground stability was evaluated with confinement effectiveness, strength-stress ratio, stress path relative to yield surface and time-dependent stress redistribution in rocks. Parametric study reveals that the inclination angle of backfilled stope reduces the confinement effectiveness in host rocks when the walls creep is minor, thus exacerbating rock mass sloughing potential. However, backfilled stope with a shallower dip angle gains superior ground stability enhancement when the creep deformation is substantial by exercising more significant compression on the backfill and effectively mobilizes its passive support performance during consolidation. More simulations were conducted to analyze the effect of stope height and width, mine depth, mechanical properties of rocks, compressibility of backfill and filling gap on the time-dependent stress redistribution and stability around the inclined backfilled stope.