Safe, Sustainable Management of Filtered Tailings
Professor Andy Fourie, project leader, The University of Western Australia
Dr Jinglong Gao, Research Associate, The University of Western Australia
- Alcoa of Australia
- The International Aluminum Institute (UK)
- Rio Tinto
- Alumina Quality Workshop (AQW) – currently represented by South32
The key objective of this project is to facilitate the widespread adoption within the mining and processing industry of filtered and stacked tailings as a viable, safe and cost-effective management strategy.
Increasingly large volumes of the residue from processing of ore are being produced, as ore grades continue to decline. The resulting waste material must be securely stored as it constitutes a potential source of contamination. Failures of tailings storage facilities are unfortunately common, with a number of catastrophic failures in recent times.
Filtering of process residue, such as red mud from the alumina processing industry, and mine tailings offer the possibility of vastly reducing the footprint of future tailings storage facilities (TSFs), of minimising potential leachate generation, thus reducing potential releases of contaminated water, and significantly improving the geotechnical stability of such facilities. This project uses standard geotechnical engineering practices, together with the utilisation of novel monitoring and quality assurance techniques to achieve a robust methodology for managing placement and compaction of filtered tailings, thus ensuring the deposit will remain geotechnically stable. Adoption of filtered residue management techniques will ultimately contribute significantly towards an ongoing social licence to operate.
The primary objective is to develop and verify a methodology for managing the deposition and compaction of filtered mine tailings to ensure long term geotechnical stability and sustainable closure of these storage facilities is achievable. Using Alcoa’s Kwinana facility, where a large filtration plant has been commissioned, as a test site, the project evaluates various techniques for evaluating the state of the filtered mine tailings (red mud) after compaction. These measurements are coupled with advanced geotechnical modelling to provide predictions of future geotechnical stability. Using the monitoring techniques developed in this project, these predictions will be constantly evaluated and verified, providing a feedback loop in order to ensure ongoing stability is ensured. Additionally, geotechnical centrifuge tests will be carried out to model the process of ‘piggybacking’, whereby a filtered material is placed (usually quite rapidly) on an existing conventional hydraulic tailings or red mud residue facility. Such an operation has many potential advantages, including improved utilisation of existing footprints, but is still unproven and has potential geotechnical instability risks if not properly implemented.
A key outcome of the project is a Monograph for use by the mining industry that describes the proposed field tests, monitoring strategies and stability evaluation techniques that, when implemented as a total residue management strategy, will ensure the stability of these deposits both now and in the long-term, i.e. post-closure.