Vacuum consolidation of soda-ash tailings

Abstract

The Solvay process, widely used in industrial production of soda ash, generates a large quantity of tailings. The tailings consist of fine solids suspended in alkaline water that remain in a loose state, causing environmental concerns. An alternative solution for the management of sodaash tailings is presented in this paper, that is, the use of a vacuum pre-loading technique to consolidate the tailings so that they can be used as a foundation material in industrial sites. This paper presents the procedure and results of vacuum pre-loading consolidation of soda-ash tailings in a field trial. A vacuum pressure of approximately 90 kPa was applied to a 45 × 45 m area to a depth of 8 m via prefabricated vertical drains. The results showed that after 66 days of vacuum pre-loading treatment, the water content of the soda-ash tailings was reduced by 12·3% to 42·4%. Also, densification was shown by changes in void ratio, unit weight and settlement. The tailings were consolidated to a material with the undrained shear strength ranging from 22·3 to 34·4 kPa, compared with the initial value of 7·1–14·5 kPa. The allowable bearing capacity of the tailings reached 120 kPa as tested from the static loading plate test. The vacuum pre-loading method has shown to be a fast, effective and economically feasible alternative for in situ consolidation of soda-ash tailings.

A comprehensive study on the effects of initial water content, suction magnitude, and drainage zone size on self-weight consolidation and vacuum preloading of soft soils and slurried mine tailings

“…Therefore, the use of ground improvement techniques for accelerating settlements or dewatering tailings compatible with project conditions is essential. For instance, the surcharge loading method for the control of settlements for lowly consolidated areas with soft uranium tailings [36], electro-osmosis method for dewatering mineral tailings (e.g., leach residue and gypsum [38]; copper sulfide tailings [39]; iron ore tailings [40]; alumina tailings [41]), and vacuum consolidation in order to manage settlements (e.g., soda ash tailings [42]; oil sands tailings [43]; fine copper tailings [44]).…”