Remote

Physical Modelling of Tailings Dam Breach: Exploring Overtopping following a Seepage Failure

ABSTRACT:

The international mining industry has experienced significant tailings dam failures in recent history creating a heightened awareness for the hazard posed by tailings storage facilities (TSF). This has illustrated the need for a more critical examination of tailings dam breach mechanisms and the potential mobility of liquefied tailings. However, much uncertainty still exists in the breach and runout analysis for TSF as available empirical-statistical runout methods are limited and commonly used breach analysis models were developed primarily for water-retaining dams.

Meg's presentation titled "Physical Modelling of Tailings Dam Breach: Exploring Overtopping following a Seepage Failure" will begin by highlighting the importance of the outflow hydrograph (the time rate of outflow during a breach event) as a boundary condition into many flood routing numerical models that inform inundation maps and emergency preparedness plans. Through her research, Meg has conducted several physical models within the large flume at Queen's University to quantify and compare breach outflow hydrographs following the loss of containment caused by a hydrotechnical failure (i.e. overtopping at a low point of the dam crest) to that experienced after geotechnical failure (i.e. seepage failure of the downstream slope caused by the closure of a toe drain). Preliminary outcomes suggest that, for the conditions tested, both mechanisms generated a similar value of peak outflow but had significantly different time to breach initiation.

Meg will also share some outcomes in matching her physical models of seepage failure to seepage analyses performed in finite element software. Using the pore pressure data and measured geometry of the dam from her physical models, Meg was able to closely replicate her results in GeoStudio to generate an understanding of the stability of the dam as failure progressed. Continued evolution of this work will occur over the next two years as she aims to increase her working database for its continued use in calibrating and validating numerical models built for the case of tailings. Meg will also introduce her next phase of research, where the newly implemented instantaneous release gate within the large flume at Queen's University will aid in the study of liquefaction to generate an understanding of the mobilized volume of material. Her presentation offers an excellent example of how a multi-institutional collaboration is necessary to tackle complex problems by bringing together a team of researchers conducting physical and numerical modelling, with lessons learned from field-case studies of tailings failure, to improve upon current practice in tailings breach and runout analyses.

BIO:

Megan McKellar (Meg) is a Ph.D. candidate in the Department of Civil Engineering at Queen's University working to further understand the initiation, breach, and runout processes of tailings storage facilities through large-scale physical models of tailings dam geometries. This work, supervised by Dr. Andy Take, is part of the wider industry sponsored CanBreach research project in collaboration with the University of British Columbia (Dr. Scott McDougall), the University of Waterloo (Dr. Steven Evans), and five industry partners: Imperial Oil Resources Ltd., Suncor Energy Inc., BGC Engineering Inc., Klohn Crippen Berger, and Golder Associates Ltd. The group of academics and industry partners at CanBreach have a focused purpose to equip engineers and dam practitioners with tools, like numerical simulations, to help manage the risk associated with tailings storage facilities. Through an integrated approach to research, the CanBreach team combines physical and numerical modelling with field and remote observations to provide a detailed exploration of the hydrological and geotechnical issues surrounding tailings dam breach and runout.