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), Paste 2009: Proceedings of the Twelfth International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 251-260, https://doi.org/10.36487/ACG_repo/963_29
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.
Aachib, M., Mbonimpa, M. and Aubertin, M. (2004) Measurement and prediction of the oxygen diffusion coefficient in
unsaturated media, with applications to soil covers, Water, Air and Soil Pollution, 156: pp. 163–193.
Bryan, R. and Simms, P. (2008) Drying and oxidation during surface disposal of paste tailings, Proceedings of the 23rd
International Conference on Solid Waste Technology and Management, Pittsburgh, Pennsylvania, USA, March
Cincilla, W.A., Landriault, D.A. and Verburg, R. (1997) Application of paste technology to surface disposal of mineral
wastes, Proceedings of the Fourth International Conference on Tailings and Mine Waste 1997, pp. 343–356.
Fisseha, B. (2008) Evaporation and unsaturated flow in multilayer deposits of gold paste tailings, Unpublished Master
of Applied Science Thesis, Department of Civil and Environmental Engineering, Carleton University, May 2008.
Fredlund, D.G. and Rahardjo, L. (1993) Soil Mechanics for unsaturated soils, Wiley, New York, 1993.
Fujiyasu, Y. and Fahey, M. (2000) Experimental study of evaporation from saline tailings, ASCE Journal of
Geotechnical and Geoenvironmental Engineering, 126: pp. 18–27.
Fujiaysu, Y., Fahey, M. and Newson, T. (2000) Field investigation of evaporation from freshwater tailings, ASCE
Journal of Geotechnical and Geoenvironmental Engineering, 126: pp. 556–567.
Shuttleworth, J.A., Thomson, B.J. and Wates, J.A. (2005) Surface disposal at Bulyanhulu – practical lessons learned,
Proceedings of the Sixth International Seminar on Paste and Thickened Tailings, R.J. Jewell and S. Barrera
(eds), Australian Centre for Geomechanics, Perth, Australia, pp. 207–218.
Simms, P., Grabinsky, M.W. and Zhan, G. (2007) Modelling evaporation of paste tailings from the Bulyanhulu mine,
Canadian Geotechnical Journal, 44: pp. 1417–1432.
Theriault, J., Frostiak, J. and Welch, D. (2003) Surface disposal of paste tailings at the Bulyanhulu gold mine, Tanzania.
In Proceedings of Sudbury 2003, Mining and the Environment, G. Spiers, P. Beckett, H. Conroy (eds),
Laurentian University, Sudbury, Canada, pp. 265–269.
260 Paste 2009, Viña del Mar, Chile