Static liquefaction and critical state mechanics of gold mine tailings subjected to different stress paths
Abstract
The mechanisms through which mine tailings fail have been the interests of many studies recently. In this series of studies, the flow liquefaction and instability behavior of gold mine tailings were examined within the framework of critical state soil mechanics. In the first study, the behavior of a gold mine tailings in stress paths involving extensional consolidation or shearing in extension was evaluated. Monotonic tests were carried out on isotropically and Ko-consolidated samples to assess the effect of stress-induced anisotropy and mode of shearing on the static liquefaction characteristics tailings. In the second study, the drained instability of two gold mine tailings under lateral stress relief was investigated. Constant deviator stress (CDS) unloading tests were performed using a triaxial apparatus to simulate instability imposed by unloading in a drained condition. Several field failures have been associated to similar mechanisms. Different techniques were employed to determine the onset of instability in CDS tests and important affecting parameters were assessed. In the third study, the effect of the presence of different percentages of non-plastic fines on the static liquefaction behavior of a given gold mine tailings was examined. The variability of fines content during compaction of mine waste and deposition of tailings slurries, even in a single tailings impoundment, highlights the possible consequences of tailings’ gradation change and fine particles presence on the behavior of such materials. In the fourth study, the capability of a critical state-based model, NorSand model, in replicating the behavior of two gradations of a gold mine tailings was investigated. The purpose was to simulate liquidation susceptibility to tailings. The ability of the model was evaluated in a numerical model of a tailings dam.