Dewatering Behaviour of Clay Slurries

Abstract

The main objective of this research was to develop a fundamental understanding of the dewatering behaviour of clay slurries. A comprehensive research methodology was developed to understand the natural dewatering processes of consolidation, desiccation and consolidation-desiccation. Laboratory investigation methods were improved, data analysis techniques were enhanced, and numerical methods were customized. An active clay slurry was prepared at different initial conditions (3 LL to 1 LL) to mimic field conditions ranging from a thin slurry to a paste-like consistency. Thin samples were used in a conventional oedometer test and in the evaporation test. A correlation was developed between the oedometer test and the bench-top centrifuge test to describe slurry consolidation. Likewise, the instantaneous profile method was applied to thin samples resulting in avoiding the need of instrumentation in evaporation tests. The small-strain consolidation theory was customized to predict large-strain consolidation deformations and diffusion equation was used to simulate desiccation. The use of effective stress and soil suction as state variables was found suitable for clay slurries. A consolidation-desiccation framework was developed to identify the governing dewatering processes operative within a slurry deposit. This research produced useful laboratory test methods, which can be implemented at on-site laboratories for determining the consolidation and desiccation properties of clay slurries. Similarly, the improved understanding of the significance of initial conditions (suspension to a paste-like consistency) on slurry dewatering is important to develop material-specific tailings deposition schemes. Finally, an understanding of the governing dewatering processes is useful to develop site-specific tailings management strategies.