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UBC Theses and Dissertations

Applications of reactive transport modeling for assessing the effects of heterogeneities and internal structure on mass loadings from waste rock piles Raymond, Katherine Elizabeth


Design strategies for waste rock piles (WRPs) to mitigate or reduce the potential for poor drainage quality which have associated environmental and economic liabilities are an important consideration for mining operations. Due to their size and complexity, conceptualizing internal processes and forecasting drainage quality from WRPs has proved challenging. Reactive transport modeling (RTM) is a tool that can help improve understanding of complex interactions of physical and geochemical processes within WRPs and compare the effects of pile design on drainage water quality. In this thesis, RTM is used to investigate the effect of physical and chemical heterogeneities, pile construction methods and scale on mass loadings in drainage from full-scale WRPs through a series of stylistic models. RTM is also applied to a laboratory-scale model to simulate an engineered cover system as part of the long-term design plan for the Tio Mine, Quebec, Canada. Results from the stylistic models indicate that heterogeneity and structural features in WRPs can cause significant variations in effluent quality, when compared to a homogeneous case. Simulated peak loadings are reduced due to the presence of heterogeneities and internal structure, at the same time prolonging the release of poor-quality drainage. The results also indicate that pile construction methods (e.g. end- and push-dumping) affect drainage release in different ways; however, these differences vanish for larger multi-lift piles. Simulations suggest that multiple lifts and the presence of buried traffic surface homogenize mass loadings, independent of construction methods. Simulations also indicate that peak mass loadings from waste rock piles are reduced by a factor of 2-3 when heterogeneities and structure are considered, which has implications for the design of water treatment systems. These results were put to practice in simulations of a laboratory-scale model, where heterogeneities proved essential for capturing effluent quality from different material zones, and for conceptualizing internal flow paths occurring within the dry cover system in place. In addition, results from this research demonstrate the capabilities of the recently developed unstructured grid code MIN3P-HPC for capturing complex shapes and geometries, which may prove useful for future investigations of capillary barrier effects and other design strategies in WRPs.

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