A case study: The seismic stability of an upstream-raised tailings impoundment (part i)

Nicolas Lemieux, Denise Leahy, Jean-François St-Laurent

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Earthquake Engineering & Geophysics

ABSTRACT: This paper presents the results of piezocone (CPT-Vs) testing and liquefaction analysis using a simplified evaluation method for an upstream-raised tailings impoundment currently under construction. The impoundment is used to contain tailings from the processing of niobium ore at Mine Niobec near the city of Saguenay in the province of Quebec, Canada. The impoundment was constructed by building two parallel starter dykes 60 meters apart along the perimeter, placing and compacting coarse tailings between the two starter dykes, and then raising the coarse tailings in the upstream direction with the width of the compacted section decreasing with height. This creates a relatively dense shell of liquefaction-resistant coarse tailings around the perimeter of the impoundment. The site lies in the seismic zone that produced the 1988 Saguenay earthquake (magnitude 5.9). This zone is capable of producing earthquakes with magnitudes as great as 7.5.

RÉSUMÉ: au piezocône (CPT-Vs) (méthode simplifiée d) de la ville de Saguenay dans la province de Québec, Canada. Le parc à résidus mesure 650 m par 1250 m et a été es de 60 m le long du périmètre, par la mise en place de résidus grossiers compactés entre les deux digues de départ et enfin, un la largeur diminue avec la hauteur. Le site est situé dans la zone sismique qui a produit le tremblement de terre du Saguenay en 1988 (magnitude de 5.9) et qui pourrait éventuellement produire des tremblements de terre de magnitude supérieure à 7.5.

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