The effect of flyash addition on the consolidation properties and shear strength of oil sands fluid fine tailings

ABSTRACT: Concern about the growing volume of fluid fine tailings resulted in the Alberta Energy Regulator setting out requirements for the disposal and closing of the tailings ponds through Directive 085, a policy document known as the Tailings Management Framework. The Tailings Management Framework policy requires oil sands companies to reduce their production and storage of fluid fine tailings (FFT) by creating deposits that can be reclaimed in a timely manner. A great number of commercial tailings technologies has been developed, many of which are mature and others are in an advanced development stage. The objective of the research reported in this paper was to investigate the effects of flocculation with flyash addition and thickening treatments by performing large strain consolidation tests and shear strength tests on treated fine tailings. The consolidation and shear strength of the treated FFT was then compared to those of untreated FFT to assess the effects of the treatments. The effect of adding flyash to the flocculent varied, but was not sufficient to achieve the required void ratios. The flyash-treated thickened tailings (TT) were less compressible than untreated TT. It appears that the flyash cements the fine tailings, increasing its resistance to consolidation. The flyash-treated TT had a much larger shear strength than untreated TT, which is an effect of the cementation of the particles.