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• W3208682827 abstract "Mine tailings production will continue to escalate rapidly due to the growing demand for commodities and reducing ore grades. Rising safety and environmental concerns from communities and regulator expectations threaten the ability of the industry to manage tailings cost-effectively. Tailings dam failures continue to occur around the world at poorly managed tailings storage facilities (TSFs), causing downstream loss of life to humans and animals, damage to infrastructure and livelihoods, and environmental impacts. Most TSFs still employ primarily physical solutions coupled with chemicals additives to enhance the physical performance of tailings in their operations. However, to date, conventional physical and chemical solutions for managing tailings are unable to meet the challenges mentioned above.The development of a comprehensive approach to tailings management, including biological solutions paired with physical and chemical solutions, presents a significant opportunity to manage tailings effectively during operations and at closure. However, little attention is devoted to biological solutions using bacteria to modify the parameters and performance of tailings because of the wide physical and chemical variability of tailings, which is directly related to the nature of the orebody and mineral processing.This thesis aims to demonstrate the improvement of tailings parameters and performance through the use of bio-additives that employ bacteria capable of inducing microbially induced calcium carbonate precipitation (MICCP), resulting in a more compact and stronger material by cementing the tailings particles. A practical multi-disciplinary approach, encompassing geotechnical engineering, geochemistry, and microbiology, is proposed to understand the entire MICCP process reaction (from biological to chemical to physical) and to demonstrate how the outcomes change tailings parameters and performance.Four different types of tailings were fully characterised and subjected to different tests to evaluate the ability of MICCP to change their parameters and performance. To assess changes in tailings parameters, microbiological techniques, chemical analyses, scanning electron microscopy (SEM), and X-Ray diffraction, coupled with conventional geotechnical tests, were adapted to resemble typical tailings conditions. This allowed the evaluation of the potential use of bio-additives in real tailings mine site applications under large-scale conditions.This thesis proposes a novel method of adapting the bacteria to tailings conditions using the process water collected from the tailings, to replicate its chemical characteristics. The process to adapt the bacteria relies on the sub-culturing method, which keeps the micro-organism alive under the tailings chemical conditions and allows bacterial growth. Meanwhile, the assessment of the relevant parameters, such as pH, electrical conductivity, and optical density, provides information to predict MICCP performance.The effect of the bio-additives on key tailings parameters was measured, at a macro-structure level, including their settling behaviour, consolidation, and shear strength. Analyses of the specific gravity, particle size distribution (PSD), and SEM images were valuable in understanding the changes that occurred at a micro-structural level. The measurements show a slight effect on settling behaviour, a significant reduction in compressibility during consolidation tests, and an increase in shear strength during vane shear testing. However, the treated tailings exhibited more brittle behaviour under ultimate strength conditions. There was little influence of the bio-additives on specific gravity. However, an increase in the tailings particle size (about a doubling of the value of D50) was observed during the PSD analyses. Also, SEM analyses confirmed the increase in the size of the particles due to CaCO3 mineral formation and the bonding of the tailings particles into larger structures. The results also confirmed that the bacteria serves as a nucleation site for CaCO3 mineral formation.Biogeochemical processes during MICCP were decoupled from the inorganic reactions to understand how time and the molar concentration of the solution impact the performance of the process and the formation of CaCO3. Triggering the reaction at 6 hours, instead of at 24 hours as hypothesised at the beginning of the research, caused the formation of CaCO3 to surge in the form of calcite over vaterite, which is positive due to the stable nature of calcite, and became a more feasible option for scaling up the application. To maximise the precipitation of CaCO3 and optimise the MICCP reaction, the ratio of urea to CaCl2 (typically 1:1) should be changed to 1.6:1.An integrative approach using the “tailings continuum concept” was developed to assess the effects of the MICCP reaction on the key parameters of tailings from an initial slurry-like to soil-like conditions, which resemble the typical evolution of tailings in a TSF. The settling, rheological, and shear strength parameters correspond to the dewatering, transport, and disposal processes of tailings management. The results indicated that it is feasible to apply the bio-additives into slurry tailings and to achieve the expected parameter changes under soil-like conditions. This shows promise not only for the potential treatment of large volumes of tailings, but also for the option of implementing an integrated solution throughout the lifecycle of the TSF from operation to closure.This work demonstrated that by using MICCP, the changes in some tailings parameters is possible and can be applied to solve some of the challenges in tailings management. For the first time, the biological process has been included to assess tailings solutions, with special consideration given to their variable nature and conditions, for potential implementation in real operational applications." @default.
• W3208682827 created "2021-11-08" @default.
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• W3208682827 date "2021-10-28" @default.
• W3208682827 modified "2023-09-25" @default.
• W3208682827 title "Sustainable Tailings Management: Improvement of Tailings Geotechnical Behaviour Using Bio-additives" @default.
• W3208682827 doi "https://doi.org/10.14264/3409e01" @default.
• W3208682827 hasPublicationYear "2021" @default.
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