Journal of the South African Institution of Civil Engineering
On-line version ISSN 2309-8775
MACROBERT, C J and BLIGHT, G E. A field study of the in situ moisture regime during active hydraulic tailings deposition. J. S. Afr. Inst. Civ. Eng. [online]. 2013, vol.55, n.3, pp. 57-68. ISSN 2309-8775.
A common method of managing tailings in semi-arid environments is to self-impound the waste as it dries. This paper presents the results of research carried out on the in situ drying behaviour of platinum tailings. Monitoring of gravimetric water contents following deposition and the quantity of water released during sedimentation indicated that a tailings beach acts as a gravitational thickener. After sedimentation, water contents were observed to decrease at a rate correlated with reference evapotranspiration, reaching a steady-state condition. Field capacity values determined from laboratory experimentation and predictive modelling correlated closely with this steady state. Further near-surface moisture reduction is inhibited due to the relative abundance of moisture rising from below to replenish deficits. Liquidity indices demonstrated that, as a result, only the head of the beach dries to a steady-state condition which provides strength to impound the tailings.
Keywords : tailings; reference evapotranspiration; moisture loss; field capacity; strength gain.