Laboratory experimental study of the evaporation and mechanical behaviour of deposited tailings.

ABSTRACT

Surface deposition has been widely used in the mining industry to manage mill tailings. Tailings are generally discharged in the form of a slurry into tailings ponds. The slurried tailings are deposited in layers that undergo complex processes, e.g. evaporation, desiccation and consolidation. The evaporation of the deposited tailings controls their geotechnical engineering behaviour, which is necessary to characterise the physical properties. In this study, a constant temperature device was employed in evaporation tests to investigate two classes of deposited tailings, and the effects of the initial concentration, particle size, exposure area and deposited layer thickness on the evaporation processes were analysed. The test results showed four stages in the evaporation processes of deposited coarse and fine tailings. Dewatering of the deposited tailings occurred during the first two stages, which were keys to improving the desiccation efficiency of the tailings in the pond. The exposure area and deposited layer thickness also had a considerable influence on evaporation. The evaporation rate increased with the exposure area and layer thickness. Direct shear tests were performed to measure the shear strength of intact tailings during evaporation and used to determine the variation law of the mechanical properties of the test tailings.