Modeling Postblasting Stress and Pore Pressure Distribution in Hydrating Fill Mass at an Early Age

Abstract

Cemented paste backfill (CPB) is a widely used porous medium to fill mined-out cavities in the subsurface due to its superior environmental and operational benefits. The stability of a retaining structure (barricade) is a crucial design factor in backfill operations as CPB is under pressure imposed by material conditions at an early age. Although field monitoring has revealed the impacts of mine-blast operations on the backfill pressure that acts on the retaining structure, current studies on stress distribution in backfilled stopes have not considered the effect of such dynamic loadings. Therefore, to analyze the redistribution of stress in backfill due to mine blasts, a total-stress viscoplastic cap model was used in this study to assess the dynamic response and generation of excess pore pressure of early-age backfill during blast loading. Next, a multiphysics model for CPB was used to assess the variations in the stress state after the blast impact in backfilled stopes during the binder hydration process of the material. The two adopted models were then validated against a series of laboratory and field experiments. Finally, they were integrated and applied to investigate the effect of drainage condition, stope size, barricade location, proximity of detonation, blast sequence, initial backfill temperature, and cement content on the redistribution of stress after blast loading in backfilled stopes. The insights obtained from the results of the study increase the understanding of the stability of retaining structures for backfills in the practical engineering conditions of mine fields.