Academic journal article Journal of Environmental Engineering and Science

Erosion Characteristics and Resuspension of Sub-Aqueous Mine Tailings

Academic journal article Journal of Environmental Engineering and Science

Erosion Characteristics and Resuspension of Sub-Aqueous Mine Tailings

Article excerpt

Abstract: The use of shallow water covers for containing sulfide bearing mine tailings in non-arid climates has gained importance over the years due largely to their effectiveness as oxygen barriers. In spite of the numerous documented benefits of these covers, some fundamental questions on the application of the technology still remain; a major one being the contribution of the nature of the tailings particles to the overall performance of the cover. Many of the existing tailings ponds have been designed assuming cohesionless sediment behavior. Total suspended solids and sediment trap measurements at some existing water cover sites, designed using the cohesionless sediment approach, have indicated significant resuspension at these sites. The present study provides information on the cohesive nature of sulfide mine tailings particles using particle size and mineralogical data and results of laboratory erosion experiments. The results show that the erosion patterns for tailings particles are similar to those reported for cohesive natural sediments. A power law erosion equation is proposed for calculating erosion rates and estimating the optimal water cover depth for flooded mine tailings.

Key words: sulfide mine wastes, subaqueous disposal, erosion character, cohesive sediments, erosion shear stress relationship.

Resume: L'utilisation de couvertures aquatiques peu profondes pour contenir les residus miniers sulfureux dans les climats non arides a gagne de l'importance au cours des dernieres annees surtout en raison de leur efficacite en tant que barriere contre oxygene. Malgre les nombreux avantages documentes sur ces couvertures, certaines questions fondamentales demeurent quant a l'application de cette technologie. Une de ces questions est la contribution de la nature des particules des residus au rendement global de la couverture. Plusieurs parcs a residus existants ont ete concus en presumant que les residus se comportent comme s'ils n'avaient aucune cohesion. Les mesures du total des solides en suspension et des sediments pieges a certains sites de couvertures aquatiques existantes, concues en considerant que les sediments n'avaient aucune cohesion, ont montre une remise en suspension importante a ces sites. La presente etude fournit de l'information sur la nature cohesive des particules de residus miniers sulfureux en utilisant la granulometrie et les donnees et les resultats mineralogiques des experiences sur l'erosion en laboratoire. Les resultats montrent que les patrons d'erosion des particules de residus sont similaires a ceux rapportes pour les sediments naturels cohesifs. Une equation d'erosion de loi exponentielle est proposee pour calculer les taux d'erosion et estimer la profondeur optimale de la couverture aquatique sur les residus miniers ennoyes.

Mots-cles: residus miniers sulfureux, deposition subaquatique, caractere d'erosion, sediments cohesifs, relation erosioncontrainte de cisaillement.

[Traduit par la Redaction]

Introduction

Over the last decade shallow water covers in engineered containment structures (also referred to as "mine tailings ponds") are becoming increasingly accepted methods for decommissioning unoxidized mine tailings (Li et al. 1997; Yanful and Catalan 2002). Although the benefits of water covers have been demonstrated in numerous field applications (Holmstrom and Ohlander 1999; Holmstrom et al. 2000; Yanful and Catalan 2002) certain aspects still require further understanding.

Mine tailings are the product of blasting, milling (grinding), and flotation (during which chemicals are added) and are different from natural sediments, whose structures are governed by weathering, transportation, sedimentation, and sorting. Depending on the milling process, tailings could be very fine and uniform. Upon settling from a suspension, mine tailings particles may result in a comparatively loose bed with higher water content than those of fine grained natural sediments, due to the relatively uniform size and shape of the particles. …

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