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Experimental and numerical evaluation of single-layer covers placed on acid-generating tailings

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doi: 10.1007/s10706-017-0185-0
Authors:Pabst, Thomas; Aubertin, Michel; Bussiere, Bruno; Molson, John
Author Affiliations:Primary:
Ecole Polytechnique de Montreal, Department of Civil, Geological and Mining Engineering, Montreal, QC, Canada
Other:
Universite du Quebec en Abitibi-Temiscamingue, Canada
Universite Laval, Canada
Volume Title:Geotechnical and Geological Engineering
Source:Geotechnical and Geological Engineering, 35(4), p.1421-1438. Publisher: Springer, Dordrecht, Netherlands. ISSN: 0960-3182
Publication Date:2017
Note:In English. Based on Publisher-supplied data. 67 refs.
Summary:This study focuses on the reclamation work being performed on two former acid-generating tailings sites, located in Quebec, Canada. At both sites, the tailings were partially oxidized due to extended exposure, and the pore water is acidic. The reclamation solution applied to control acid mine drainage is a monolayer cover, made of non acid-generating tailings in one case and a till in the other. The goal of this project was to assess the response of the tailings-cover systems under various conditions. Tailings samples were collected in situ and characterized in the laboratory. Large column tests were conducted to evaluate the hydrogeological and geochemical behaviour of the covered tailings following wetting and drying cycles. The instrumented columns were designed to reproduce some of the existing site conditions and provide representative results for longer term analyses. Volumetric water content, suction, and oxygen concentrations were also monitored over time. The experimental data were used to validate different numerical models including those constructed with Vadose/W (GeoSlope Int.). Additional simulations were conducted under field conditions to evaluate the effect of various influence factors such as the depth of the water table, climatic conditions and the thickness of the cover. The combination of experimental and numerical results show how the behaviour and efficiency of a monolayer cover placed over reactive tailings depend on these factors, highlighting the importance of hydrogeological properties and water table depth. In many instances, the cover materials were prone to desaturation, especially when the water table was deeper than about 2 m below the tailings-cover interface. These results tend to indicate that relatively thin monolayer covers would not be able to prevent oxygen ingress under some of the conditions observed in the field. Desaturation of the cover and/or reactive tailings is due to a combination of drainage and evaporation. In such cases, increasing the thickness of the monolayer cover only has a limited effect. A discussion follows on the practical implications of these laboratory experiments and the numerical simulations for field design of reclamation measures at these two tailings impoundments. Copyright 2017 Springer International Publishing AG and Springer International Publishing Switzerland
Subjects:Acid rock drainage; Dams; Experimental studies; Ground water; Hydraulics; Laboratory studies; Mine waste; Numerical models; Oxidation; PH; Pore water; Reclamation; Tailings; Tailings dams; Thickness; Unsaturated zone; Water table; Canada; Eastern Canada; Quebec
Record ID:802113-10
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute. Reference includes data supplied by Springer Verlag, Berlin, Federal Republic of Germany
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