Volumes of Dam Material Mobilized by Erosion During Tailings Dam Failure Events
Authors: Daniel Adria1, Violeta Martin1, Heleman Wong1
Conference: Tailings and Mine Waste 2024
Date: November 10-13, 2024
1 Knight Piésold Ltd., Canada
ABSTRACT
The breach size and shape, and the rate at which it is formed, are key characteristics that must be estimated for conducting a dam breach analysis. A frequently used simplification in such analysis is that the breach channel through a dam is trapezoidal in cross section. This convention allows for consistent comparison between historical dam breaches (water and tailings dams alike) and is useful for numerical modelling of the breach hydrograph and downstream flood wave or runout propagation. However, a breach channel is three-dimensional, and an assessment of the volume of the dam material mobilized for a given twodimensional trapezoidal breach geometry represents an additional useful parameter to consider when conducting the breach analysis.
The breach geometry and the mobilized dam volumes in a tailings dam breach event could vary substantially depending on the construction type, the dam geometry, and the construction materials used. The breach characteristics can also be impacted by the breach mechanism, which appears to be different for erosional type mechanisms (i.e., overtopping and internal erosion) compared to non-erosional type mechanisms (e.g., slope instability, foundation failure, liquefaction). It is important to include such considerations when conducting tailings dam breach analyses, as they may present physical constraints for the breach development.
Two empirical equations for calculating the eroded dam volume and the dam erosion rate are presented in this paper. Multiple linear regression equations were developed for a combination of historical erosional breach events of water and tailings dams, which use the breach height and the breach outflow volume as inputs. Also presented is a method to estimate whether the supernatant pond volume is sufficiently large for an erosional breach to progress to the foundation based on these equations.
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