Effects of Relative Density in Progressive Sliding of Tailings deposits: Insights from Flume Tests

Abstract

We present a series of flume tests to observe the process of tailings slope failure when subjected to a concentrated water flow. Progressive flow slides were observed in a range of tailing deposits with varying relative densities, in which hydraulic conductivity reduced with increasing relative density. Slope densification by compaction of very loose or loose tailings deposits can lead to a lower permeability, generating excess pore pressure, and subsequently reducing slope stability. This is evident from the great number of acoustic emission signals before sudden failure, and from a sharp increase in the surface displacement and internal displacement observed after excess pore pressure generation. The variation of fluid-pressure distribution results in successive sliding, onset at the toe and progressing from the toe to the rear of the slope. Excess pore pressure generation is found to occur after, rather than prior to sliding, and it only occurs along the slip surface. An optimal relative density of 0.35 was identified, in which the slope failure changes from a sudden collapse to a progressive failure. However, the optimal relative density may vary with the height of the slope. This research extends existing knowledge about behavior of tailings materials, while the observed discrepancy between the failure mechanisms of slopes made of loose and dense deposits could provide insights for preventing failures of tailings dams.