Laboratory Study of Freeze-Thaw Dewatering of Albian Mature Fine Tailings (MFT).

摘要

Tailing ponds in Northern Alberta has covered an area of 170 km 2. Directive 074 issued in 2009 set stringent criteria for tailings reclamation. Freeze-thaw dewatering is one of the most promising approaches for dewatering MFT as one cycle of freeze-thaw can release up to 50% pore water. In this research, freezing tests were conducted with different temperature boundaries. A lower freezing rate induced higher solids content and higher undrained shear strength. In addition, finite strain consolidation tests were performed on both as-received and frozen/thawed MFT. Freeze-thaw decreased the compressibility to about half that of as-received MFT and increased the permeability to 6 times that of asreceived MFT with the same void ratio. Both compressibility and permeability curves converged at higher effective stress (sigma'=100 kPa). The coefficient of consolidation of frozen/thawed MFT was larger at lower effective stress and smaller at higher effective stress, comparing with that of as-received MFT. These results can be used to predict the field behaviors of Albian MFT and optimize the application of freeze-thaw dewatering.