Dynamic imaging and modelling of multilayer deposition of gold paste tailings

Abstract

Surface deposition of paste or thickened tailings is increasing contemplated as an alternative to conventional slurry deposition. One important challenge in managing paste is to predict the evolving geometry of the tailings stack during deposition. This study dynamically images multilayer deposition of paste in flows in flume and axisymmetric flows. Each layer is left to self-weight consolidate for a day before the next layer is placed. It is found that both the steady-state profiles and the dynamic flows can be modelled as a Bingham fluid using equations developed from lubrication theory. Yield stress and viscosity were determined using rheometry and slump tests. It is shown that the yield stress obtained from the slump test may overestimate the yield stress of significance to flow deposition; namely that yield stress that characterizes when the tailings stop flowing. The lubrication theory equations show that the overall angle of a tailings deposit at steady-state is dependant on the scale of the flow, which may explain the discrepancy between laboratory flume angles and field angles noted in practice.