Authors: Violeta Martin, Daniel Adria, Heleman Wong
Conference: 90th Annual Meeting of the International Commission on Large Dams
Date: May 27-June 3, 2022

SUMMARY

The Mount Polley, Fundão, Feijão and other tailings dam failures have had catastrophic environmental and social impacts. Tailings dam owners, operators, regulators, and stakeholders rely on dam breach studies to evaluate potential consequences of a failure and make informed decisions and ultimately safeguard the public. However, scientific understanding of the breach processes and physical phenomenon of tailings outflows is still developing. Uncertainties in model inputs combined with lack of standardized methodologies for completing the various analyses required for these complex studies present considerable challenges to professionals. Experience and judgement must be relied on to construct tailings dam breach models and assess the results.

Tailings dam breaches typically result in hyperconcentrated flows due to the mobilization of stored tailings solids. After determining the hypothetical outflow volume and the breach hydrograph, the breach outflow is routed downstream using hydrodynamic or geomechanical modelling tools to estimate the inundation. Site-specific tailings rheology is required to characterize these flows, which is rarely available. This paper describes recent experiences with modelling the flood wave propagation of non-Newtonian tailings dam breach outflows using hydrodynamic modelling tools. Challenges encountered and lessons learned from various case studies are discussed, including availability and quality of input data and selection of appropriate models for the given conditions. All these factors have profound impacts on the results.

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