Authors: Miskolczi, I; Zhan, G; Keller, J

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Miskolczi, I, Zhan, G & Keller, J 2023, 'A novel modeling approach coupling post-closure tailings storage facilities draindown and water balance simulations ', in B Abbasi, J Parshley, A Fourie & M Tibbett (eds), Mine Closure 2023: Proceedings of the 16th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth,

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Traditional methods of tailings management involve spigotting or cycloning tailings slurry into large tailings storage facilities (TSF). The draindown of entrained TSF water at closure can take decades to centuries and requires careful management. As a result, knowledge of the evolution of the TSF draindown rate in time and duration of active management in closure and post-closure is an important cost consideration for mine closure optimization. Predicting TSF draindown typically employs a numerical or an analytical approach based on unsaturated flow principles. The complexities of tailings solution flow dynamics may be more rigorously predicted by a numerical model compared to an analytical model. However, incorporating solution management alternatives, such as recirculation to the surface of the TSF, is not feasible in the numerical modelling codes commonly used today. A well-calibrated analytical model, even with simplified water flow dynamics, may still be able to reproduce draindown as accurately as a numerical model, but also allows unlimited flexibility in evaluating water management methods. We propose using a combination of numerical modelling and analytical modelling to predict the time required to achieve passive water management. Variability in tailings properties, TSF geometry, and the time dimensionare considered in the numerical model, which is coupled to an analytical model that allows feedback of typical water management methods. The analytical TSF water balance model includes the calibrated flux curve and incorporates water management elements such as seepage recirculation, passive and forced evaporation, effect of the shrinking pond surface, and effect of the closure cover construction. An example of the method applied to the Nevada Gold Mine’s Gold Quarry mine in Nevada is described in this paper, detailing the assumptions that were made with respect to the closure water balance and the functional parameters used for modelling the final draindown of the TSF.

Keywords: tailings, closure, water management, draindown

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