Authors: Perotti, DA; Gitirana Jr, GFN; Fredlund, MD

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Perotti, DA, Gitirana Jr, GFN & Fredlund, MD 2019, 'Analysis of dry cover systems composed of tropical soils for mining waste', in AB Fourie & M Tibbett (eds), Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 579-592,

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The flow of water in mining tailings and waste rock may cause serious environmental impacts associated with acid rock drainage. Soil cover systems have been used to control or minimise such damages. In relatively dry climates, ‘store-and-release’ covers, also known as dry covers, have been considered as feasible alternatives. The objective of this paper is to evaluate the influence of atmospheric conditions and soil type in the performance of dry cover systems, considering conditions typical of tropical climates found in Brazil’s centralwest region. Numerical analyses using the finite element method were performed considering four different systems composed of tropical soils. Among the proposed arrangements, three use a soil that presents a bimodal soil–water characteristic curve and the fourth cover employs a unimodal soil. The thicknesses of intermediate materials were varied, and different representative precipitation parameters were considered for a period of one year. The results obtained were compared in terms of the internal flow and the capacity of the system to store water. The results indicate that bimodal soils may not be ideal cover materials and require specific compaction conditions that would reduce their macropores. Unimodal tropical soils presented adequate response as store-and-release materials. The use of an intermediate layer acting as a capillary barrier did not offer significant improvement to the cover systems evaluated.

Keywords: cover systems, dry covers, tropical soils, finite element method

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