A numerical study of the effect of wick drains applied in mine stopes with paste fill

Abstract

Paste fill is popularly used in underground mines. A large amount of water is added into fills to facilitate their pipe transportation. Upon placement, the self-weight consolidation in paste fill can lead to the generation of excess pore-water pressures. To avoid excess pressures applied on the retaining structure, filling is usually staged with an undesirable curing interval. Recent numerical analyses conducted by the authors indicated that pre-installing wick drains in backfilled stopes can accelerate the consolidation, and thus enable continuous filling. In previous analyses, however, a zero pressure head was imposed along the wick drains and the effect of third dimension was ignored. These tend to overestimate the fill’s consolidation. In this paper, more representative numerical models are performed with GeoStudio, with the three-dimensional drainage around a wick drain converted to an equivalent plane-strain condition. Moreover, the fill permeability in the drift is reduced, compared to that in the stope, to mimic the restricted flow via the drawpoint. The results show that the consolidation of paste fill depends largely on the wick drain layout (spacing). The effect of wick drain size is also evaluated.