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The use of the resistivity piezocone (RCPTU) for the geoenvironmental characterization of sulphide bearing tailings and native soils

University of British Columbia

Recent advances in the in-situ testing of sulphide bearing mine tailings have included the development of a resistivity piezocone (RCPTU) and improved water sampling technologies. The RCPTU measures the bulk resistivity of the soil, in addition to all other standard piezocone (CPTU) measurements. The bulk resistivity profile permits assessment of pore water chemistry with correlation to pore water samples and the standard CPTU measurements give accurate estimates of stratigraphy and key geotechnical parameters and hydrogeological characteristics. Also, use of the RCPTU in combination with discrete pore water sampling technologies can permit the development of relationships between bulk resistivity measurements and specific pore water constituents. The technology is repeatable, rapid and economical when compared to traditional drilling and sampling site investigation techniques. A significant area of concern in the mining industry is acid rock drainage (ARD). ARD is the contaminant drainage which results from oxidation of sulphide minerals and it can represent a serious hazard to surrounding surhcial and groundwater systems. The evolution of ARD creates elevated electrical conductivity of tailings pore water which can be readily detected by the RCPTU bulk resistivity measurements. In addition to environmental issues, there are significant geotechnical considerations in the construction of large dams for tailings storage. One fundamental consideration is the potential for a flow failure of the tailings impoundment due to liquefaction of the tailings under both static and dynamic loading conditions. There is a significant challenge in adequately characterizing these impoundments for their geochemical, hydrogeological and geotechnical nature. The potential to use a single procedure for determining many varied engineering design parameters is highly attractive. Results of a field testing program carried out at sulphide bearing tailings impoundments of three Canadian mines are presented with respect to environmental and geotechnical characterization issues. Site-specific relationships between bulk resistivity measurements and pore water chemistry are developed. CPTU data is used to assess hydrogeological characteristics at specific sites and estimate movement of ARD contaminated pore water. CPTU-based methods are used to assess the susceptibility of liquefaction of tailings, considering both static and dynamic load conditions. Finally, recommendations are made with regard to the use of the RCPTU as a component of an overall geoenvironmental characterization plan for the evaluation of sulphide bearing tailings impoundments.

Thesis/Dissertation

application/pdf

2009-02-17

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http://hdl.handle.net/2429/4705

Civil Engineering

University of British Columbia

UBCV

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