Characterisation of unsaturated geotechnical properties of filtered magnetite tailings in a dry stack facility

Abstract

Filtered tailings and dry stacking are gaining attention due to problems with slurry-deposited tailings facilities and consequent catastrophic failures around the world. Factors such as recent technological advancements in filtration, lack of water, regulatory pressures and societal demands are shifting focus towards dry stacking. With the growing attention to filtered tailings, a major challenge is the knowledge gap on unsaturated soil properties required to understand the performance of unsaturated tailings in the dry stack facility, especially the hydraulic and shear strength behaviours. This paper presents details of investigations to characterise unsaturated properties of filtered tailings material in a large-scale dry stack facility located in a highly net positive evaporation area in Western Australia. Field and laboratory tests were conducted to understand (i) hydraulic and water retention/storage functions, and (ii) shear strength responses to relevant stress state variables. Historical cone penetration tests with pore pressure measurements (CPTus) conducted annually between 2013 and 2017 consistently indicate negative pore pressures within the dry stack up to 25 m depth.

Operational strategies to improve paste plant performance

“…Under Atterberg testing, the cake can be classified as being close to the liquid limit. Tailings are reported to have liquid limits at 25-26% moisture and plastic limits of 18-20%, which coincides with the range of moistures produced in vacuum filtration (Amoah et al 2018). The mixing units are at the upper end of the technology scale at 500 t/hr.…”

Iron Ore Tailings Dewatering: Measurement of Adhesion and Cohesion for Filter Press Operation

“…Improved process water management and safer storage reduce costs and are an impossrtant aspect in terms of sustainable mining. For this reason, the number of filtered tailings solutions is steadily increasing [5] and larger and larger plants are being operated [6].…”

Stress-strain behaviour of unsaturated compacted coal rejects and tailings

“…[9]), largely in the context of tailings storage facilities. In contrast, it seems that testing of tailings under unsaturated conditions is fairly recent and not many results are reported in the literature [11][12][13]. Vo and coworkers [14] specify that this is particularly the case for coal tailings.…”