Dewatering Behaviour of Fine Oil Sands Tailings

An Experimental Study

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Oil sands tailings are a warm aqueous suspension of sand, silt, clay, residual bitumen and naphtha. The tailings are hydraulically transported and stored in tailing ponds where they segregate, with the sand settling from suspension forming beaches and the remaining tailings flowing to the middle of the pond. After several years of tailings disposal, three layers have developed in the pond, which are, from top to bottom, water, thin fine tailing and mature fine tailing (MFT). MFT is the major reason that the tailing ponds cannot be reclaimed. Due to low the high water content and low hydraulic conductivity, MFT consolidate very slowly in the ponds. Therefore, many technologies have been proposed remove the water from the tailings and increase the consistency so that the tailing pond can be reclaimed. but most of these dewatering technologies are rejected due to the limited technical or economic feasibility. In this PhD thesis, two potential fine tailings management technologies were described. These two technologies were: (1) sub-aerial drying of fine tailings deposited in thin lifts, and (2) use of prefabricated vertical drains (PVD) in enhancement of consolidation of fine tailings in the pond. In this PhD project, experiments were carried out to investigate geotechnical properties and dewatering behaviour of fine oil sands tailings related to the described technologies.