available for gravity transportation, and water is inexpensive. On smaller dams the practise of pumping tails along the crest to relocatable cyclones is energy efficient, however it can be difficult to ensure the sands have the correct geotechnical properties for dam integrity with multiple remote hydrocyclones. As dams become larger centralised cyclone stations ensure better control of the sand quality at the expense of transport, pipeline losses in high density sand transport pipelines are significant and wear can be high. Both methods rely on good drainage in the dam to ensure water required in the transport is effectively removed to prevent liquefaction. Hydraulic transport is efficient and economical when water is readily available, but it poses the greatest risk in tailings dams. Sand Yield and Quality With changes in mineral processing, ore types and declining grades there has been a trend to grind the ore more finely. In addition, the size of mining operations and their tailings dams is increasing resulting in higher lifts, larger dams and a higher quality of sand requirement. This trend is reducing the ratio of sand yield from the tailings and pushing the requirement for better control of sand quality. Particularly when clays are present the control of hydrocyclones is limited. Where the requirements and quality control of a cyclone sand construction material for the dam wall requires sharper cuts that contain less slimes, current technologies might struggle. Operators may be required to utilise borrow material at higher costs for the construction of tailings dam walls when suitable properties cannot be achieved with cyclone sand. Alternative production and transport Trials were conducted to evaluate the effectiveness of producing sands for dam construction from a tailing that is high in clay and has struggled to achieve the required sand properties. The plan was to take sand from a cyclone underflow and feed it to a dewatering screen, underflow from the screen would be in turn cyclone again with the underflow returning to the screen and the overflow returned to the tailings dam. Dewatering screen The screen selected (LH0918-1) is a linear motion horizontal single deck screen designed for dewatering. The ultra fine screen decks were selected with a focus to remove fine particles and water. Dewatering screens are an energy-efficient technology with intrinsic classification and dewatering properties. The cut size is less affected by feed conditions for removing water from the structural zones of the ore.
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