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

Abstract

Backfill is routinely adopted as a ground support measure for underground mines. However, ground stability enhancement by backfill has received limited research attention. This is likely to be because of the conventional assumption that the fill material exhibits a significantly lower stiffness than the host rocks. Significantly, a recent pioneering work revealed the time-dependent ground stability around a backfilled stope with vertical walls through numerical modeling. In practice, underground stopes typically exhibit a higher or lower degree of inclination. This alters the stress state in peripheral rocks and may induce severe instability and dilution, particularly in stope-hanging walls. Hence, it is imperative to analyze the time-dependent ground stability of inclined backfilled stopes for backfill structure design. Therefore, comprehensive numerical simulations were performed using FLAC3D to address this knowledge deficiency by incorporating a coupled analysis of the backfill consolidation behavior and long-term creep deformation in surrounding rocks. The ground stability was evaluated based on the confinement effectiveness, strength–stress ratio, stress path relative to the yield surface, and time-dependent stress redistribution in the rocks. A parametric study revealed that the inclination angle of the backfilled stope reduced the confinement effectiveness in the host rocks when the wall creep was minor. This exacerbated the rock mass sloughing potential. However, a backfilled stope with a shallower dip angle achieved superior ground stability enhancement when the creep deformation was substantial, by applying a more significant compression on the backfill and effectively mobilizing its passive support performance during consolidation. Additional simulations were conducted to analyze the effects of stope height and width, mine depth, mechanical properties of rocks, backfill compressibility, and filling gap on the time-dependent stress redistribution and stability around the inclined backfilled stope.

Keywords

inclined backfilled stope / ground stability / time-dependency / creep / consolidation

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