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Numerical modelling of transfer processes in a waste rock pile undergoing the temporal evolution of its heterogeneous material properties.

Lahmira, Belkacem; Lefebvre, René (2015). Numerical modelling of transfer processes in a waste rock pile undergoing the temporal evolution of its heterogeneous material properties. International Journal of Mining, Reclamation and Environment , vol. 29 , nº 6. p. 499-520. DOI: 10.1080/17480930.2014.889362.

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Résumé

Waste rock piles producing acid mine drainage (AMD) are complex and heterogeneous unsaturated systems in which multiple coupled processes are involved: multiphase flow of fluids (liquid and gas), heat transfer and mass transport. Numerical modelling is required to consider together these processes. Such modelling was used to evaluate the effects of closing options for a waste rock pile, including resloping and the placement of a cover, on AMD production from the South Dump of the Doyon Mine (Quebec, Canada). The thermal data recorded within the pile during 15 years show a steady reduction of temperature over the last 10 years. The objective of this study was to numerically reproduce the temporal evolution of thermal conditions to answer two key questions: (1) Can the evolution of material properties over time explain observed changes in thermal conditions? (2) If waste rock properties have evolved, is it effective to cover the pile to mitigate AMD production? Modelling showed that reducing the permeability of materials in the model can reproduce observed temperature changes over time, which cannot be achieved by reducing the reactivity of materials. Results also show that the evolution of hydraulic properties of the waste rock pile can have a direct effect on the global oxidation rate because of their control over the supply of atmospheric air and oxygen in the pile. When the production of AMD is already in decline, simulations also show that a simple remodelling of the surface may be sufficient to significantly decrease the oxidation rate and provide immediate environmental gains, without a cover. However, there may be other benefits related to cover placement that have not been evaluated by our study, especially in relation to the management of water runoff and leachate.

Type de document: Article
Mots-clés libres: acid mine drainage; waste rock; multiphase fluid flow; heat transfer; low-permeability covers; numerical modelling
Centre: Centre Eau Terre Environnement
Date de dépôt: 18 avr. 2018 18:49
Dernière modification: 18 avr. 2018 18:49
URI: http://espace.inrs.ca/id/eprint/3614

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