Unsaturated soil behaviour in thickened and filtered tailings

Abstract

Proper application of unsaturated soils to thickened or filtered tailings has substantial potential to optimise such tailings deposition. Unsaturated behaviour bears on both the geotechnical and geo-environmental performance of these deposits. Geotechnically, there is an increase in strength through both additional densification, and the presence of suction, as well as a stress history effect. The latter is especially important to understand in situ measurements in previously desiccated deposits; geo-environmentally, unsaturated behaviour strongly bears on seepage generation, as well as management or mitigation of acid generation. This paper summarises a body of work on experimentation, numerical simulation, and field data relating to different aspects of unsaturated behaviour and their relevance to practical outcomes for design of thickened or filtered tailing deposits. An important new outcome from this summary is the suggestion to characterise the extent of the stiffness imparted by drying, especially due to the possible risk of strength loss in thick deposits when the tailings eventually yield under self-weight.