Fisseha, B, Bryan, R & Simms, P 2009, 'Evaporation, Unsaturated Flow and Oxidation in Multilayer Deposits of Gold Paste Tailings', in R Jewell, AB Fourie, S Barrera & J Wiertz (eds), Proceedings of the Twelfth International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 251-260.
The behaviour of surface deposited paste mine tailings is strongly influenced by the evaporation and
saturated-unsaturated flow through the tailings, which not only controls desiccation, but also governs salt
accumulation and oxidation. Select data is presented from a series of drying tests on multilayer deposition of
a gold paste tailings. During drying, rewetting after precipitation, and interlayer flow after placement of
fresh layer, including small scale tests (0.15 m diameter column tests) and large scale tests (1.7 x 1.7 m in
plan) were undertaken to study unsaturated flow and evaporation from two-layer deposits of two gold paste
tailings. It is shown that the interlayer flow after addition of the second layer can be reasonably modelled
using unsaturated flow codes. Though significant cracking occurred during drying of the paste tailings, its
effect on the rate of evaporation was minimal. In some of the tests, the accumulation of salt at the surface
substantially suppressed the rate of evaporation. The accumulation of salts could be tracked by sampling the
surface of the tailings and measuring the electrical conductivity of the pore-water. Mass transport could be
qualitatively modelled by one-dimensional contaminant transport theory. Profiles of sulphide oxidation with
depth and time are also presented. The degree of oxidation is shown to be small but significant, and can be
reasonably approximated by oxygen diffusion modelling coupled to the unsaturated flow codes.
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(eds), Australian Centre for Geomechanics, Perth, Australia, pp. 207–218.
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260 Paste 2009, Viña del Mar, Chile