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An investigation into the use of agglomerated tailings in backfill : a potential tailings disposal option and case study for Eskay Creek Mine, British Columbia Chovan, Karen

Abstract

This paper details an investigation into the feasibility of using agglomerated tailings in a 'dry' aggregate fill for underground mining. A test program began with the agglomeration of tailings materials from Eskay Creek Mine, British Columbia, using Portland cement as a binding agent. Thereafter, a series of backfill tests were conducted in which agglomerates, river aggregate, and tailing materials were combined in various proportions to develop a high quality fill. The results of the investigation showed that it is technically feasible to utilize agglomerated tailings in an aggregate backfill used for structural support in underground mining operations. Three related factors reveal their importance: grain size distribution, the degree of compaction and the void content of the mixture. These variables, among others, significantly affect the strength and quality of the fill - for example - the lower the void ratio, the greater the strength of the fill. The strengths of the individual constituents and the water to cement ratio also play major roles in determining the fill strength, but only in those cases where the materials are compacted to minimize voids. The effects are an increase in strength with the increasing strength of the constituents and with decreasing water/cement ratio. Where the void content of the aggregate mix is high, the effect of changing the water to cement ratio is minimal. Although the process of agglomeration is technically feasible, it seems that the associated costs are in opposition to its implementation. An economic analysis of the agglomeration process has revealed that other methods of disposal such as using a tailings pipeline are significantly more attractive from a financial viewpoint mainly because such an option allows the removal of the tailings filter from the process (now in use at the mine). However, the presence of mercury, antimony and arsenic in the tailings raises health and environmental concerns; the need to insure that ARD generation and the release of heavy metals after mine closure is unresolved. In mining situations where ARD generation is an issue, the agglomeration concept may be technically feasible, although the agglomerates may require sealing with a reagent such as sodium silicate, however testwork is required to verify the efficacy of this concept. Where ARD generation is not suspected and where surface or submarine disposal are not viable, the use of agglomeration is a technically feasible alternative.

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