Evaluation of the water retention curve of mine waste rock using laboratory tests and predictive models

Anna Peregoedova, Michel Aubertin, Bruno Bussière

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Mining Geotechnics

ABSTRACT: of the water retention curve of mine waste rock using laboratory tests and predictive models Anna Peregoedova École Polytechnique de Montréal, Montréal, Québec, Canada Now with Ministère du Développement durable, de l'Environnement et de la Lutte contre les changements climatiques, Québec, Canada Michel Aubertin École Polytechnique de Montréal, Montréal, Québec, Canada Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, Québec, Canada Bruno Bussière Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, Québec, Canada ABSTRACT The water retention curve (WRC) of waste rock sampled from a pile at an open pit mine was determined in the laboratory by means of drainage tests in large instrumented columns. The testing procedure is described in the article and the main results are presented. The WRC measured on specimens with different maximum grain sizes is characterised by a low air entry value (AEV < 10 cm) and low residual suction (r < 40 cm). The residual volumetric water content was observed to be somewhat larger than expected (r = 0.06-0.08), due to the presence of a widely graded fine-grained fraction. The experimental data imply that such waste rock drains rapidly at small values of the matric suction, and easily reaches a residual state where moisture remains in the finer pores. The experimental results have led to modifications of the predictive MK model that enable a better estimate of the WRC of waste rock. RÉSUMÉ La échantillons prélevés sur la halde à stériles été évaluée essais de drainage réalisés dans de grandes colonnes instrumentées. La procédure expérimentale et les CRE mesurée sur plusieurs fractions granulométriques montre des < 10 cm) et de la succion résiduelle (r < 40 cm). La teneur en eau volumique résiduelle de ces roches stériles est (r = 0,06-0,08) en raison de la présence dfraction fine à granulométrie étalée. Ces résultats indiquent que ces roches stériles se drainent rapidement à de faibles succions et atteignent facilement un état résiduel. Ces mesures ont aussi menées à des modifications du modèle ur la CRE. 1 INTRODUCTION Surface disposal of mine waste rocks in piles can induce significant environmental impacts, especially when contaminated effluents are generated by reactive minerals. It is well known that water flow through porous materials like waste rock is strongly influenced by the degree of saturation. An appropriate assessment of the distribution and movement of water within a pile is not possible without obtaining reliable hydrogeological properties of the waste rock, including its saturated hydraulic conductivity (ksat) and water retention curve (WRC). These parameters are required to conduct numerical simulations aimed at evaluating water flow and related transport processes in waste rock piles (Fala et al. 2005, 2006; Molson et al. 2005; Broda et al. 2013; Dawood and Aubertin 2014). It is however quite a challenge to evaluate these properties (Smith and Beckie 2003; Aubertin et al. 2005, 2008; Milczarek et al. 2006; Bussière et al. 2011) and to assess the flow conditions in such piles (Morin et al. 1991; Smith et al. 1995; Eriksson et al. 1997; Nichol 2002; Dawood et al. 2011; Fala et al. 2013). Experimental data on hydrogeological properties of waste rock under saturated conditions were reported in Peregoedova et al. (2013). This paper presents laboratory testing results on the determination of the water retention curve of the same waste rock by means of intermediate scale drainage tests conducted in large instrumented columns. The WRC obtained experimentally are used to propose modifications to the predictive MK model (Aubertin et al. 2003) that enables a better representation of the influence of the widely graded particle size distribution (PSD) of these waste rocks. As discussed by Peregoedova et al. (2013), the waste rock tested appears to include a system of interconnected and highly conducting macropores. This aspect is briefly discussed in relation with the possible impact of preferential water flow on the hydraulic conductivity function. 2 TESTING METHOD The tests were conducted on samples taken from one of the waste rock piles at the Lac Tio mine (RTFT), located

RÉSUMÉ: ation of the water retention curve of mine waste rock using laboratory tests and predictive models Anna Peregoedova École Polytechnique de Montréal, Montréal, Québec, Canada Now with Ministère du Développement durable, de l'Environnement et de la Lutte contre les changements climatiques, Québec, Canada Michel Aubertin École Polytechnique de Montréal, Montréal, Québec, Canada Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, Québec, Canada Bruno Bussière Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, Québec, Canada ABSTRACT The water retention curve (WRC) of waste rock sampled from a pile at an open pit mine was determined in the laboratory by means of drainage tests in large instrumented columns. The testing procedure is described in the article and the main results are presented. The WRC measured on specimens with different maximum grain sizes is characterised by a low air entry value (AEV < 10 cm) and low residual suction (

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Anna Peregoedova; Michel Aubertin; Bruno Bussière (2014) Evaluation of the water retention curve of mine waste rock using laboratory tests and predictive models in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper247,author = Anna Peregoedova; Michel Aubertin; Bruno Bussière,title = Evaluation of the water retention curve of mine waste rock using laboratory tests and predictive models ,year = 2014}