Gopalakrishnan, V, Nester, T, Mgumbwa, J & Holtzhausen, W 2018, 'Harvesting tailings from an active tailings storage facility: success and challenges – Frog’s Leg mine, Evolution Mining', in RJ Jewell & AB Fourie (eds), Proceedings of the 21st International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 337-350.
This paper is an investigation report summarising a series of tests and observations conducted over a two year period as part of a feasibility study for replacing the tailings used in the cemented paste fill (CPF).
The testworks were conducted at Evolution Mining’s Frog’s Leg mine, Kalgoorlie, which utilises undercut longhole stoping with CPF.
The project was initiated after the tailings reclaim agreement with a third party supplier failed to be negotiated, which compelled management to explore the possibility of harvesting tailings from Evolution’s Mungari Gold Operations’ (MGO) newly established tailings storage facility (TSF). The feasibility study includes testing tails for CPF compatibility and liaising with TSF engineer(s) for the best extraction of tails without hindering the dam lift cycle and stability.
Access towards the centre of the TSF was an issue due to poor compaction of the surface near the decant point and this, in turn, restricted the amount of tails that could be extracted. Tailings with a fine particle size were required to reduce the void ratio in the CPF; however, these tailings had deposited towards the middle of the TSF, which was wet, resulting in the harvested tails containing excess coarse size particles.
A combination of insufficient tailings available to meet the annual paste backfill requirements and the lack of fines in the tailings lead to the concept of adding screened oxide (overburden) to the extracted tails.
This paper explores the blending of oxide with tailings for CPF mix at different ratios and its effect on the final CPF product. The key findings from the study concluded that the strength of the CPF will be inversely proportional to the ratio at which the oxide is added to the CPF mix.
Keywords: tailings, harvest, blending, cemented paste fill (CPF), particle size distribution
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