Settling and consolidation behaviour of coal tailings slurry under continuous loading

Tailings are generated as the fine-grained wastes on the washing of run-of-mine coal to meet market specifications. Coal tailings are typically sand-sized and finer, and are pumped as an aqueous slurry at a solids concentration of typically 25% solids by mass, conventionally to a surface tailings storage facility. The physical processes that coal tailings undergo on sub-aerial disposal to a surface tailings storage facility include beaching, hydraulic sorting, settling, self-weight consolidation and desiccation. The settling and consolidation of coal tailings, the topic of this paper, have the most profound effect on the volume that the deposited tailings occupy. These processes are particularly important where the rate of rise is rapid and/or deposition is under water. Settling occurs in the upper part of the recently deposited tailings layer, while consolidation occurs simultaneously towards the base of the layer. The two processes of settling and consolidation are conventionally tested separately in the laboratory; settling in a column and consolidation in a consolidometer. This paper describes a purpose-built, large, slurry consolidometer, in which coal tailings slurry is added in three layers at a nominal 25% solids by mass, allowed to settle between layers, and consolidated under three different continuous loading sequences. Thus the two processes of settling and consolidation are carried out in the same testing apparatus, from an initial consistency representative of field conditions.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe