Improved model-based study of backfill stress distribution considering rock-backfill closure, mine depth, and position along stope length

Abstract

During upward horizontal stratified backfill mining, stable backfill is essential for cap and sill pillar recovery. Currently, the primary method for calculating the required strength of backfill is the generalized three-dimensional (3D) vertical stress model, which ignores the effect of mine depth, failing to obtain the vertical stress at different positions along stope length. Therefore, this paper develops and validates an improved 3D model solution through numerical simulation in Rhino-FLAC^3D, and examines the stress state and stability of backfill under different conditions. The results show that the improved model can accurately calculate the vertical stress at different mine depths and positions along stope length. The error rates between the results of the improved model and numerical simulation are below 4%, indicating high reliability and applicability. The maximum vertical stress (σ_{zz, max}) in backfill is positively correlated with the degree of rock-backfill closure, which is enhanced by mine depth and elastic modulus of backfill, while weakened by stope width and inclination, backfill friction angle, and elastic modulus of rock mass. The σ_{zz, max} reaches its peak when the stope length is 150 m, while σ_{zz, max} is insensitive to changes in rock-backfill interface parameters. In all cases, the backfill stability can be improved by reducing σ_{zz, max}. The results provide theoretical guidance for the backfill strength design and the safe and efficient recovery of ore pillars in deep mining.

Keywords

backfill / mine depth / rock-backfill closure / stability / maximum vertical stress / numerical simulation

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Central South University