Authors: Dadashi, A; Bussière, B; Wilson, GW

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Dadashi, A, Bussière, B & Wilson, GW 2023, 'Geochemical and hydrogeological behaviour of commingled mixtures of tailings and waste rock', in GW Wilson, NA Beier, DC Sego, AB Fourie & D Reid (eds), Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings, University of Alberta, Edmonton, and Australian Centre for Geomechanics, Perth, pp. 693-703,

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The conventional method of segregated disposal of tailings and waste rock is associated with several environmental problems, especially acid rock drainage (ARD) which is a challenging and crucial issue. Previous studies have shown that mixing tailings and waste rock can potentially decrease ARD potential. However, there are limited studies that quantify the effect of mixture ratio of waste rock and tailings on the water quality. This study presents a developed methodology to design and test different waste rock and tailings mixture ratios through leveraging particle packing theory for binary mixtures. The mineralogy and chemical properties of the mixtures is first presented. Three columns of mixture materials were mounted for a series of leaching tests over a period of about two years to experimentally simulate the impact of different mixture ratios on the water quality. The preliminary results of the leach column tests demonstrate that the ratio of waste rock and tailings of the commingling mixtures influences the unsaturated hydrogeological behaviour and the water quality. The study also provides fundamental data to investigate the hydrogeological and geochemical behaviour of the tailings and waste rock mixtures. The approach used in this study can be implemented to determine an optimised mixture ratio to minimise ARD and alleviate the damaging environmental impacts of segregated disposal.

Keywords: acid rock drainage, commingled tailings and waste rock mixtures, leaching column tests

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