Electroosmotic treatment of sand washery tailings and the improved geotechnical characteristics

Placement of soil covers over slurry deposited tailings, which are typically characterised by poor undrained shear strength involves significant risks and challenges, from the geotechnical viewpoint. Dewatering by means of applying an electric current, also referred to as electroosmotic (EO) dewatering technology is known to improve weak soil deposits. A laboratory study was undertaken to study the improved geotechnical characteristics of electroosmotically treated (EO treated) material through testing of sand washery tailings. To this end, EO dewatering experiments were carried out at varying voltage gradients using a purpose built EO cell. The properties of the EO treated tailings, including strength and compressibility characteristics were then characterised using laboratory element testing such as direct simple shear and oedometer tests to compare with the typical characteristics of untreated material. The results indicated that EO treatment increased the preconsolidation pressure of the tailings by three to nine times in the cathode region and six to fifteen times in the anode region, depending on the adopted voltage gradient. Owing to the overconsolidation effects induced by the EO treatment, strength gains of up to 664% were observed in the anode region of the experiment conducted with the maximum voltage gradient of 150 V/m.