Waste rock inclusions in filtered tailings storage facilities to improve their hydrogeotechnical and geochemical stability

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One of the most critical issues faced by the mining industry is the management and safe disposal of the large quantities of mine wastes generated by the operations, and in particular tailings, which are fine-grained materials produced during the processing and concentration of ore minerals. Despite technical developments in the last decades, geotechnical instabilities still regularly occur like at the Mount Polley Mine, in 2014 (British-Columbia, Canada), or at the Bento Rodrigues mine (Mariana province, Brazil), in 2015. Although reasons for failures are numerous, they typically involve water. Dewatering improves the geotechnical properties of tailings and reduces the needs for confinement structures and, thus, the risk for instabilities. Filtered tailings especially present many advantages over traditional slurry tailings, like an improved water recovery and recirculation, a reduction of the geotechnical risk and consequences of dam failures, rapid consolidation and trafficability, and progressive reclamation. However, the long-term evolution of the water content in filtered tailings exposed to climatic conditions, the exposure to oxygen and the risk for contaminated mine drainage generation if the tailings are reactive, and the possible lixiviation of contaminants present in pore water, raise some questions about the applicability of the technique in humid climates. This research project aims to evaluate these risks and the performance of an innovative solution based on the use of waste rock inclusions (WRI) in filtered tailings storage facilities to improve their geotechnical long-term stability and control contaminant transport. The proposed research program includes field work, physical models in the laboratory and numerical simulations and optimization. The outcomes will include practical solutions to improve long-term stability of filtered tailings storage facilities and will be of great interests for mining companies considering filtered tailings disposal, in Canada and elsewhere.