Triaxial behavior of thickened gold mine tailings samples prepared by hydraulic deposition

M. Nuth

Dans les comptes rendus d’articles de la conférence: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: ENERGY RESOURCES - I Mining and Tailings

ABSTRACT: Thickening of tailings is getting an increasing attention as it provides a sustainable solution for the storage of mining wasterock. Indeed, the thickening of tailings provides a more solid consistency that allows forthe tailings to be stacked with agreater beach angle than conventional tailings. The combination of this method with the upstream raising method resultsin the possible reduction of the footprint of the deposit.In this paper is presentedan experimentaltesting programon theshearing behaviour of gold mine tailings, thickenedto a solid contents of 50% to 77%. Multiple hydraulic deposition testshave been performed inasettling column (700 mmhigh) equipped with pressure transducers to assess the consolidationprocess and the density profile of the tailings. Hydraulic deposition has also been used to deposit samples into a mold fortriaxial tests. The density values obtained at the bottom of the columns and in the triaxial mold were remarkably similarand repeatable. Consolidated Undrained shearing tests were performed in a triaxial apparatus on the samples preparedby hydraulic deposition, and compared with other sets of triaxial results performed on the same material, but moist tampedinto the mold. The deposited samples exhibited significantly higher density values than the moist tamped ones, and theshear strength properties were significantly higher.R‡SUM‡L…utilisation des r•sidus miniers •paissisoffre un mode degestion des parcs — r•sidus miniersbeaucoup plus durable. Eneffet, les r•sidus •paissis sont d•pos•s — un plus haut pourcentage solide ce qui donne la possibilit• d…empiler le r•sidu —des angles plus •lev•s que les r•sidus conventionnels. La combinaison de cette technologie et du rehaussement parl…amont rendre possible la r•duction de l…empreinte environnementale laiss•e par les parcs — r•sidus.Cet article pr•senteune s•rie de tests exp•rimentauxsur le comportement au cisaillement des r•sidus provenant d…une mine d…or. Les r•sidus•tudi•s sont •paissis — un pourcentage solide variant entre 50 et 77%. Des essais de d•position en colonne ont •t•effectu•s sur une colonne de 700 mm de haut dans le but de connaitre les densit•s aux bas de la d•position. Les essaisde colonne sont instrument•s d…un capteur de pression pour conna–tre lafin de la consolidation. Par la suite, la mƒmecolonne est utilis•e pour pr•parer les •chantillons dans le moule de l…appareil triaxial. Ainsi, les densit•s des essaistriaxiaux sont connues suite —l…analyse des essais de colonne. Des essais triaxiaux consolid•s non-drain•s sur les r•sidusminiers d•pos•s hydrauliquement ont •t• faits et compar•s avec des •chantillons pr•par•s par damage humide. Les•chantillons pr•par•s par d•position montrent des densit•s et des valeurs de r•sistance au cisaillement sup•rieures.1INTRODUCTIONOver the past decades, the mining industry has improveditscapacities to extract low grades of ore at low cost. Theseimprovements has led to greater challenges for themanagement of tailings in term of quantities. Usingconventional tailings management fortailings storagefacilities (TSF) in lower grade of oresmay lead to higherdams and larger footprint. The conventional methods fortailings disposal is described by transporting the tailings asa slurry in the TSF which is an impoundment surroundedby dams and dykes(Bussi⁄re 2007).The initial solidcontent of the conventional slurry is between 25% and45%. It is now understandable that the low solid contentadded with the extraction of low grades of ore conduct tothe retention of bigger pond of toxic wastes water and moresolid mine wastes. Bulky TSF contributes to raise the riskof larger catastrophic events i.g. greater devastatingpotential on a greater area(Bowker & Chambers 2015).The major problem with the conventional tailings was theenormous quantities of water to retain especially when thiswater is mixed with heavy metals and toxic chemicalproducts.Both theIndependent Expert and Review Panel(2015)andBoger(2012)propose the use of densifiedtailings as saferway to manage tailings. Densified tailingsmeans that at its initial deposition the tailings have a highersolid content. Thickened tailings, paste tailings and filteredtailings are the three different kind ofdensifiedtailings(Bussi⁄re 2007).In the present paper, the researchfocusesonly on thetechnology of thickened tailings (TT). According toBussi⁄re(2007)and Fourie(2012),TT correspond to atailings between 50 and 70% solid. TT was firstlyaddressed in the year 1970 by Robinsky. He presents thisnew technology as a better approach than the traditionalone toward environment(Robinsky 1975).Since thedevelopment of TT, very little has been done to

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