Analysing the effects of waste rock inclusions on tailings consolidation: Laboratory tests and modeling of the large scale in situ behavior

Frédérick L. Bolduc, Michel Aubertin

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Mining Geotechnics I

ABSTRACT: Theconstructionofwasterockinclusions(WRI)intailingsimpoundmentconsistsinstrategicallyplacingtheWRIinsidetheimpoundmentduringitsoperationtoforminternalcells.Inthispaper,theauthorsinvestigatetheeffectsofdrainagefrominclusionsontailingsconsolidationduringfillingoftheimpoundmentusinglaboratorytestingdataandnumericalsimulations.Themaintestsconductedontailingsandwasterocksarebrieflypresentedwithkeyresults.Theseprovidethepropertiesusedforthenumericalanalysesthatfollow.Acrosssectionofaportionofthetailingsimpoundmentcontaininganinclusionisthensimulatedusingafiniteelementcode.ThenumericalcalculationsshowtheextentoftheWRIinfluenceontailingsconsolidation.Additionalresultsillustratetheeffectofthemostimportantfactors.RÉSUMÉLaco-dispositiond™inclusionsderochesstériles(IRS)àl™intérieurd™unparcàrésidusconsisteàplacerstratégiquementlesIRSàl™intérieurduparcdurantsonopérationdemanièreàformerdescellulesinternes.Danscetarticle,lesauteursanalysentleseffetsdedrainagedusauxinclusionssurlaconsolidationdesrésidusdurantleremplissagedubassinàl™aidededonnéesexpérimentalesetdesimulationsnumériques.Lesessaisontfournilespropriétésdesrésidusetdesrochesstérilesutiliséesdanslesanalysesnumériques.Unesectionduparcàrésiduscontenantuneinclusionaétésimuléeparlaméthodedesélémentsfinis.Lescalculsnumériquesmontrentl™ampleurdel™influencedel™inclusionsurlaconsolidationdesrésidus.Desrésultatsadditionnelsillustrentl™effetdedifférentsfacteurs.1INTRODUCTIONSecurestorageoftailingsfromhardrockminescanbequitechallengingbecauseoftheircomplexproperties,1990;Aubertinetal.2002;Bussière2007).Amodifieddisposaltechniquehasbeenproposedtoreducethegeotechnicalandgeo-environmentalrisksassociatedwiththeconventionalsurfacestorageofminewastes.Thisnovelapproachconsistsinplacingwasterockinclusions(WRI)insidethetailingsimpoundmenttoformcompartments(orcells)inwhichthetailingsarestored(Figure1).Thisreduces,oreliminateinsomecases(forundergroundminesespecially),theneedtostoreseparatelywasterocksandtailings.Suchinclusionsofferpreferentialdrainagepathwaystodissipatetheexcessporewaterpressureduetoprogressivefilling,asthehydraulicconductivityofwasterocksisaboutthreeordersofmagnitudehigherthanthatoftailings.Wasterockinclusionscanthusincreasetheconsolidationrate,densityandshearresistanceoftailings.Thiseffectissomewhatsimilartotheaccelerationofclayeysoilsconsolidationbyhorizontaldrainageusingverticaldrains(Barron1948;Hansbo1981;IndraratnaandRedana1997;Leo2004;Tanetal.2008).Thehigherstiffnessandshearstrengthofwasterockinclusionsalsoserveasreinforcement,andthesecouldsignificantlyreducetheriskofinstabilityortheamountoftailingsreleasedinthecaseofabreach(JamesandAubertin2010,2012).Figure1:Schematicillustrationofatailingsimpoundmentwithwasterockinclusions(afterJamesandAubertin2010)Thistypeofco-disposalofwasterocksandtailingsisarecentadditiontotheoptionsthatexistforminewastemanagement(JamesandAubertin2010),andassuchitconstitutesanewresearcharea.Workontailingstestedonaseismicsimulator(Pépinetal.2012)andconceptualnumericalmodeling(Jahouaretal.2011;JamesandAubertin2012;Jamesetal.2013)havedemonstratedsomeoftheadvantagesoftheapproach,whichisnow

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