Tailing migration though geomembrane holes

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Management of mine tailings (waste generated after resource extraction) in both a safe and environmentally acceptable manner is essential for continued activity in this important sector of Canada's economy-worth $57B in 2014. Increasingly, the long-term discharge of contaminants from the tailings into the environment requires assessment. Recent research by the applicants and industry partner KCB-enabled by NSERC-demonstrated the significant benefit of using a geomembrane liner at reducing subsurface seepage from the tailings into the surrounding environment. Industry funding was used to conduct first-of-their-kind experiments to measure leakage (fluid flow through a hole in the geomembrane) for a range of practical conditions, while NSERC funding was used to conduct measurements to investigate local soil behaviour and detailed numerical analysis to understand the measured flows. Engineers can now use this new knowledge to calculate leakage for practical cases where filter compatibility between the tailings and underlying foundation soil is certain. Industry now needs to know what may happen in the many more practical cases when there may be some migration of soil particles from the tailings into the foundation soil. The proposed research will use industry funding to conduct fundamentally new experiments to assess mobility of tailings for marginally stable cases; in other words, within the "grey-area" of conventional filtration theory, does some migration of tailings fines through the geomembrane hole lead to locally-stable conditions or catastrophic loss of tailings? NSERC funding will be used to: provide more detailed insight into the mechanisms of fines migration (most likely different to conventional filtration theory because of the more complex flow pattern and large variation is seepage velocities near the geomembrane defect), quantify of how far tailing fines migrate into foundation soil, and examine how local but stable fines migration affects the leakage rate. The new research will enable more effective and economical environmental protection for mine tailings management and will provide advanced training for a Masters and an undergraduate student.