Daliri, F, Kim, H, Simms, P & Sivathayalan, S 2012, 'Contribution of desiccation to monotonic and cyclic strength of thickened gold tailings – not the same as over-consolidation', in R Jewell, AB Fourie & A Paterson (eds), Proceedings of the 15th International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 73-83.
In many jurisdictions, regulators are concerned with remobilisation of high unbounded deposits of mine waste residuals, such as thickened tailings stacks. Consequently, the monotonic and cyclic behaviour of thickened tailings is of significant interest to practitioners of mine waste geotechnique. Thickened tailings are known to gain strength through a combination of hindered settling, desiccation, and consolidation post-deposition. This paper reports on the effects of over-consolidation ratio (OCR) and desiccation, investigated using a simple shear apparatus (NGI type). Samples for element testing were obtained from laboratory tests simulating multilayer deposition in columns or flumes. In each test, tailings were deposited at some initial solids concentration and allowed to desiccate to different values of water content, both above and below the shrinkage limit. These tailings were then overlaid with fresh tailings, and allowed to resaturate by capillary action from the fresh layer. Tailings from the bottom layer were then extracted using thin-wall Shelby tube. Some tailings were allowed to settle, subsequently extracted with no desiccation, and mechanically over-consolidated. Very sharp differences in both the quantitative and qualitative behaviours of samples prepared by these two methods were observed. Mechanically over-consolidated samples exhibited high peak strengths, whereas desiccated samples exhibited much lower strengths at phase transformation, but substantial strain hardening past phase transformation. This information is very important to geotechnical practitioners working on thickened tailings projects, as many operate under the assumption that desiccation is analogous to mechanical over-consolidation.
Al-Tarhouni, M., Simms, P. and Sivathayalan, S. (2009) Seismic behaviour of thickened gold mine tailings, in Proceedings 12th International Seminar on Paste and Thickened Tailings (Paste09), R.J. Jewell, A.B. Fourie, S. Barrera, J. Wiertz (eds), 21‒24 April 2009, Viña Del Mar, Chile, Gecamin Limited, Santiago, Australian Centre for Geomechanics, Perth, pp. 291–300.
Al-Tarhouni, M., Simms, P. and Sivathayalan, S. (2011) Cyclic behavior of reconstituted and desiccated samples of thickened gold mine tailings, Canadian Geotechnical Journal, Vol. 48(7), pp. 1044–1060.
Bishop, A.W. (1959) The principle of effective stress, Teknisk Ukeblad, Vol. 106(39), pp. 859–863.
Cifuentes, L.A. and Verdugo, R. (2009) in Proceedings 12th International Seminar on Paste and Thickened Tailings (Paste09),
R.J. Jewell, A.B. Fourie, S. Barrera, J. Wiertz (eds), 21‒24 April 2009, Viña Del Mar, Chile, Gecamin Limited, Santiago, Australian Centre for Geomechanics, Perth, pp. 313–323.
Daliri, F., Simms, P. and Sivathayalan, S. (2011) A comparison of different laboratory techniques to simulate stress and moisture history of hard rock mine tailings, in Proceedings of Tailings and Mine Waste 2011 Conference, November 2011, Vancouver, B.C., Canada., Keevil Institute of Mining Engineering, Vancouver, B.C., pp. 163–175.
Fisseha, B., Bryan, R. and Simms, P. (2010) Evaporation, unsaturated flow, and salt accumulation in multilayer deposits of a paste gold tailings, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 136, No. 12, pp. 1703–1712.
Fredlund, D.G. and Morgenstern, N.R. (1977) Stress state variables for unsaturated soils, Journal of Geotechnical and Geo-environmental Engineering Division of American Society of Civil Engineers, Vol. 103, pp. 447–466.
Kim, H., Daliri, F., Simms, P. and Sivathayalan, S. (2011) The influence of desiccation and overconsolidation on monotonic and cyclic shear response of thickened gold tailings, in Proceedings 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, October 2011, Toronto, Canada, Electronic proceedings (paper 765). Canadian Geotechnical Society.
Lu, N. and Lukos, W.J. (2006) Suction Stress Characteristic Curve for Unsaturated Soil, Journal of Geotechnical and Geoenvironmental, Vol. 132, No. 2, pp. 131–142.
NRC (1985) National Research Council. Liquefaction of soils during earthquakes, National Academy Press, Washington, D.C.
Simms, P., Dunmola, A., Fisseha, B. and Bryan, R. (2010) Generic modelling of desiccation for cyclic deposition of thickened tailings to maximize density and to minimize oxidation, in Proceedings 13th International Seminar on Paste and Thickened Tailings (Paste2010), R.J. Jewell and A.B. Fourie (eds), 3‒6 May 2010, Toronto, Canada, Australian Centre for Geomechanics, Perth, pp. 293–301.