The development and design of thickened tailings discharge methods – a review

Abstract

The development of the thickened tailings disposal technique presents a new paradigm in tailings disposal. It results in a total revision of the risk profile of a tailings storage facility (TSF), and may provide significant savings in both cost and water consumption. The method was developed by Robinsky (1975), who identified that thickening the tailings stream would create a non-segregating slurry and that a steeper overall beach angle could be achieved. The outcome is the elimination, or the substantial reduction in size of retaining embankments. This has obvious benefits.The paper reviews the development history, and the key design and behavioural parameters that are needed for thickened tailings schemes, with an emphasis on the understanding of the fundamental geotechnical issues. Brief historyThe concept of thickened tailings storage was developed in Canada in the early 1970s by Robinsky (1975Robinsky ( , 1999. He identified that thickening the tailings stream sufficiently would create a non-segregating slurry i.e. hydraulic sorting would not occur on a sub-aerial beach, and that a steeper overall beach angle would be achieved. These properties permit tailings to be 'stacked', either as a low conical hill on flat ground, referred to as central thickened discharged (CTD), or as down-valley discharge (DVD).There are now about thirty known thickened discharge schemes operating worldwide (with some that have now closed). These are summarised in Figure 1, based on data presented in Williams et al. (2008). This figure is limited to schemes that are (or have been) fully operational, and are referenced in the literature or details are known to the authors.

Characterisation of a thickened tailings beach

“…The perceived, desirable characteristics of a thickened tailings beach have been discussed previously by a number of authors, e.g. Robinsky (2000), Williams et al (2003), Jewell and Fourie (2006), Williams et al (2008), Seddon and Dillon (2009), and Seddon and Williams (2010).…”

“…The importance of evaporative drying is that it applies a pre-consolidation pressure (suction) to the tailings at shallow depths. This results in significant density and strength gains in these layers, before they are covered by subsequent deposition (Seddon & Williams 2010). The deposited tailings then remain over-consolidated until the depth of burial increases to the extent that the overburden stress exceeds the equivalent drying suction.…”