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Developing models that mimic real world conditions is challenging. In many cases, data to suitably quantify the behaviour of the materials in question are unavailable to the designer, and assumptions must be made. This can lead to an overly conservative model, which in turn results in conservative and most likely more expensive solutions. This is of particular of relevance to the closure of tailings storage facilities, where costs can increase significantly from estimates made during project initiation and operations.
In arid Western Australia, in situ moisture content and matric suction measurements of the desiccation and re-saturation cycles of sulphide nickel tailings have been collected over a period of about two years. A laboratory column experiment has also been carried out to mimic the deposition and drying cycles and provide additional data, under controlled conditions, to estimate the ponding depth required to infiltrate through the full depth of desiccated tailings. These data were used as a basis to develop a preliminary cover design model, in which the desiccated tailings are incorporated into a store and release cover system, minimising the need for additional cover materials and resulting in a significant economic saving to the mine. The key outcomes of the preliminary model are presented, along with a general description of the parameters required to develop similar models.
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