Numerical assessment of potential thermal degradation of permafrost in Northern Canada due to open pit mining and tailings impoundment

A. Booshehrian, R. Wan, G. Su

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Cold Regions II

ABSTRACT: The potential thermal impact on permafrost due to surface mining activities at the proposed Kiggavik project in Nunavut, Canada, is assessed. In order to study the thermal behaviour of permafrost, a finite element based heat flow model with phase change in porous media is developed. The model is first calibrated against subsurface temperature data collected over the past several years in boreholes near the site penetrating completely into the permafrost. The transient heat simulations are conducted using the calibrated n-factors and other material properties to determine the ground temperatures, whereas tailings material was assumed to be placed at a temperature of +10ºC. The results of numerical studies of the open pits in the Kiggavik project indicates that backfilling of the open pits with warm tailings results in the formation of only small talik areas around and at the bottom of open pits, and the majority of ground material will remain frozen during the operational period.

RÉSUMÉ: On évalue l™impact des effets thermiques sur le pergélisol potentiellement causés par des activités minières en surface dans le projet Kiggavik propose au Nunavut, Canada. Afin d'étudier le comportement thermique du pergélisol, on développe par éléments finis un modèle de transfert de chaleur avec changement de phase dans un milieu poreux. Dans un premier temps, le modèle a été calibré à partir des mesures de températures en profondeur dans le pergélisol collectées pendant plusieurs années. On utilise des facteurs-n et autres propriétés matérielles après calibration dans une analyse transitoire de transfert de chaleur du sous-sol. On considère que le dépôt des résidus miniers se fait à +10ºC. Les simulations numériques des mines à ciel ouvert proposées dans le projet Kiggavik démontrent que le dépôt de résidus miniers provoque l™occurrence de petits ‚taliks™ en dessous des mines. Par contre, la majeure partie du sous-sol reste gelée pendant la période d™exploitation de la mine.

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Cite this article:
A. Booshehrian; R. Wan; G. Su (2013) Numerical assessment of potential thermal degradation of permafrost in Northern Canada due to open pit mining and tailings impoundment in GEO2013. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoMon2013Paper728,author = A. Booshehrian; R. Wan; G. Su,title = Numerical assessment of potential thermal degradation of permafrost in Northern Canada due to open pit mining and tailings impoundment ,year = 2013}