South32 Worsley Alumina Pty Ltd operates several bauxite residue storage facilities at their refinery in Western Australia. The bauxite residue slurry is thickened and pumped onto the storage facilities which are constructed on an upstream basis using compacted earthfill embankments. BRDA 5 is the newest of the residue storage facilities, established in 1999, and has a current maximum height of embankment slope of 42 m, of which a compacted earthfill starter embankment makes up the first 22 m. Since 2010, the residue has been treated after deposition using amphirols, which assist in dewatering and compacting the residue. As part of their residue management commitments, Worsley undertook a dam break analysis entailing a review of all available geotechnical testing data, a fault-event analysis to evaluate the probability of removal of support to the residue through slope instability, overtopping, geotechnical piping or failure of a buried structure leading to liquefaction of the residue and a dam break. To model the flow of the liquefied residue, pilot-scale dam break testing was carried out from which estimates of the rheology of the residue were made. The rheology has been incorporated into a flow slide model that applies stream power entropy theory to define the energy changes due to viscous effects and frictional resistance. Benchmarking of the results against modelling using computational fluid dynamics has been made. This paper presents an overview of the dam break assessment process and results that covers a liquefaction potential assessment, a semi-quantified risk assessment based on a fault-event analysis approach, rheological testing of liquefied consolidated residue in a specially developed box rheometer and probabilistic modelling of the dam break, the outflow hydrograph, and the flow inundation areas. It is concluded that incorporation of rheology representative of liquefied consolidated residue in dam break modelling results in significantly reduced prediction of inundation area.
Olympias Mine is operated by Hellas Gold S.A., a subsidiary of Eldorado Gold Corporation. The orebody shape and size are suitable for a drift and fill mining method. The mining sequence is overhand and the demand for backfill strengths are generally low except for the initial sill cuts. The design fill strengths are determined from the planned stope exposures to allow for safe extraction of the ore in adjacent drifts and immediately below the initial sill drifts with minimum dilution. Due to the permit constraints imposed on mining at Olympias Mine, after an environmental impact assessment, there is a requirement that the final backfill strength must reach a uniaxial compressive strength (UCS) of 4.0 MPa at 28-day cure age. By developing a suit of mix recipes incorporating superplasticiser admixtures, it was possible to achieve the strength demands and the workability of the backfill. This paper presents the results from comprehensive test work conducted on whole mill tailings and cyclone mill tailings to produce high strength backfill.
This paper covers FLSmidth KREBS® pump development, over the past 10 years, of an extensive range of highpressure centrifugal slurry pumps for multistage applications. The primary objective has been to produce safe, economical, energy efficient and maintenance friendly centrifugal slurry pumps to fulfil the expanding requirements of the mineral processing industries in the long distance transportation of tailings and mineral slurries. Two ranges of pumps have been developed, a double cased pump (based on the KREBS rubber lined slurryMAX XD pump) and an unlined white iron cased pump (based on the millMAX pump). The logic behind the development of the two pump ranges will be explained in depth covering the design and first article production, getting it right. The methodology of the hydraulic and structural criteria requirements that are considered during the pumps design are integrated with the use of computational fluid dynamics and finite element analysis to ensure that the pumps perform safely, reliably and with maximum efficiency. Application of the pumps to projected operating data is explained taking into consideration specific needs for flange and foundation loads, maintenance and condition monitoring. Consideration of slurry rheology and its implication on pumping performance is discussed. Cost comparison between actual field data and the theoretical positive displacement (PD) costs, as presented at the 21st International Seminar on Paste and Thickened Tailings, will be analysed in the Appendix.
The perceived need for accurate and reliable methods of measuring suspension rheology in real time arises from the greater demands being placed on mineral processing operations. To extend mine life and reduce TSF footprint the adoption of finer grinds, higher solids concentration and high clay ores result in complex multiphase suspensions that need close monitoring to optimise thickener performance, pipeline transport and tailings deposition. Often the control of the processing or transport of these suspensions can be related to its rheology. However, due to the involved nature of rheological measurement for suspensions and the nuanced interpretation of data necessary to produce useful decisions, rheometry has only seen limited application in process monitoring. A robust unit that can measure, analyse and interpret the rheology of a process stream continuously and unattended is needed. The CSIRO has developed an online rheometer to address this problem. This paper describes the process prior to the deployment of the online rheometer to an Australian goldfield site, comparing online rheological measurement to benchmark laboratory values.
Until mid-2020, the Newmont Éléonore mine cemented paste backfill (CPB) recipes were chosen from charts comparing binder contents and strengths at specific curing ages up to 56 days. However, these charts were based on Mitchells method using Éléonores biggest stope dimensions. They also did not consider any rheology, maximum surface pump pressure capacities or mix density. Using the new system, and its resulting template, backfill personnel can tailor a recipe for each stope to meet the latest sequence and environment conditions. This paper explains how the new paste recipes are selected, as well as the costs savings and productivity increases they enabled.
The disposal of diluted tailings in dams, due to their muddy state, becomes inherently difficult to contain and this poses a high risk to society, as observed in the last two accidents that occurred in Brazil in 2015 and 2019. Therefore, the disposal of coarser tailings becomes more relevant because besides contributing to the reduction of water consumption and environmental impact, it will also require a smaller disposal area. However, to transport a thicker slurry, the viscosity and the yield stress of the tailings will increase. Therefore, for long distance conveying systems, high friction losses are generated in the pipeline. In view of the high operating pressures and the low experience with these pumping systems, it is important to consolidate the hydraulic model used in the design. The loop test setup in this case was used to support the selected hydraulic model. Based on data from a loop test set up at a Brazilian mining company located in the Iron Quadrangle (Quadrilátero Ferrífero), the study proposes to validate the Hanks & Dadia (1971) model using yield stress correction according to the Buckingham equation presented by Abulnaga (2002). In the loop test, the fine iron ore tailings were pumped using positive displacement pumps. The viscosity of the tailings varied between 0.013 and 0.017 Pa.s and the yield stress between 31 and 42 Pa. Very close results were observed between the actual data from the loop test and the head loss calculation by the Hanks & Dadia (1971) model using the yield stress correction, according to the Buckingham equation.