Dam Breach Tailings Runout Analysis

A key component in risk assessment of a tailings dam is the potential runout distance or the extent of flow of tailings, which provides a main basis to determine the potential downstream impacts in the event of a tailings dam failure. Dam breach inundation studies for water storage dams generally model the extent of water flow beyond the dam. Tailings from oil sand mines are a soil mixture of water, clay, silt, sand and residual bitumen produced during the extraction process. The analysis techniques for water storage dams may not be appropriate to be used directly for the analysis of flow of mine tailings because the nature of the flow of tailings typically shows different rheological behaviour than water.

In this paper tailings runout distance assessment of a typical tailings containment dam was conducted using MADflow. Tailings with typical solids content was modelled as a flowslide material in undrained condition. The model results show that the key factors that affect runout distance of a tailings flow include undrained shear strength properties of the tailings at the onset of instability, the post-failure (liquefaction) undrained shear strength of the tailings, and the slope of the runout path downstream of the dam. Sensitivity analyses were conducted to provide a range of runout distance of tailings based on the combination of a range of likely tailings strength parameters and also compared to the extent of water flow. The use of appropriate tailings deposition and operational management activities can increase the tailings strength parameters, which in turn shorten the potential runout distance and reduce the potential hazard and risk of a dam breach.

Chen, H.J. and D.E. Becker. 2014. “Dam Breach Tailings Runout Analysis,” in CDA 2014 Annual Conference, Banff, Alberta, October 4-9, 2014. Canadian Dam Association.

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