Design, Construction, and Performance of 'Passive' Pressure Relief Wells for Tailings Dam Remediation

Xiteng Liu, Anjan Kundu, Edward Chong

In the proceedings of: GeoManitoba 2012: 65th Canadian Geotechnical Conference

Session: T2D - Seepage and Hydrogeology

ABSTRACT: Artesian conditions were observed at the downstream toe of a bauxite tailings (red mud) dam after a few years of tailings deposition. The situation worsened with the rising of tailings levels. Piezometers were installed to study the extent of the artesian zone and its impact on dam safety. Some remediation measures were carried out in the past but were found to be relatively ineffective. During the recent dam raise, a pressure relief system consisting of and toe drains was adopted to mitigate the artesian conditions. Artesian water is discharged into the system under its own pressure rather than pumping. Compared against conventional pressure relief wells, the 'passive' system eliminates the need for pumps and permanent well casings at each individual well location. This paper discusses the design considerations, the construction, and the performance of the 'passive' pressure relief system.

RÉSUMÉ: Les conditions artésiennes ont été observées au pied de la digue en aval d'un barrage de résidus de bauxite (boues rouges) après quelques années de dépôts. La situation s'est aggravée avec la hausse des niveaux de résidus. Des piézomètres ont été installés afin d'étudier l'étendue de la zone artésienne et l'impact sur la sécurité des barrages. Certaines mesures d'assainissement ont été réalisées, mais ont été relativement inefficaces. Lors de l'augmentation récente de la digue, un puits de secours de pression passif en combinaison avec des drains au pied de la digue ont été plutôt que par pompage. Comparé aux puits de surpression conventionnels, le système passif élimine le besoin de pompes et de boyaux à chacun des puits. Cet article aborde les considérations de conception, de construction et la performance du système pression passif.

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