Combined Evaporation and Freeze-Thaw Effects in Polymer Amended Mature Fine Tailings

Abstract

Evaporation and freeze-thaw phenomena are known to contribute to dewatering and densification of fine tailings streams generated from oil sands bitumen extraction.This thesis reports on studies of 1-Dimensional freezing of polymer-amended mature fine tailings that have different stress histories with respect to degree of desiccation by evaporation and self-weight consolidation. Freezing is accomplished using an electric cooling plate specially mounted in an insulated column. Polymer-amended tailings are placed at a lift of one half-meter, which has been allowed to consolidate. Temperature is recorded using thermocouples, while the densification and dewatering is tracked by monitoring of water content, pore water pressure, and cryo-suctions. After one freezethaw cycle is applied, the samples are cored and then loaded to examine differences in consolidation behaviour post-freezing. Results with respect to dewatering indicate that desiccation and one freeze-thaw cycle enhanced the dewatering process and increased the average solids content of the tailings by 6% when compared to MFT that only underwent consolidation. Also, when comparing the self-weight consolidation and desiccation phases for the three Column Tests, it was found that desiccation increases the efficiency of the freezing process. Lastly, no significant differences in compressibility and permeability properties were found between tailings that underwent just self-weight consolidation and tailings that underwent self-weight consolidation and one freeze-thaw cycle.iii