In mine tailings dam failures, the flowing material often consists of a mix of water and multiple solid phases with different sediment size classes, organic content, chemical solutes, and metals, combined with numerous sediment types in the dam itself. Some deposits can also be completely dry. The high-speed flow generated by the dam break can entrain soil from the existing terrain and, under low energy conditions, can deposit or stop altogether.
To determine the areas that could be impacted in tailings dam break events, it is critical to utilize models that consider rheology formulations that represent the dam materials and tailings, whether dilute or dry. Also, if conditions require, the model should be able to incorporate the interaction of the tailings flow with existing water bodies such as water reservoirs or rivers.
In this paper, we demonstrate the critical importance of knowing the tailings rheological characterization through the application of a 2D-Two-phase non-Newtonian numerical model.
The application involves the failure of a tailings dam considering a granular rheological formulation that represents dry tailings deposits. In the granular model, the friction angle is the stability basal angle of the material that is approximately equivalent to the free surface angle once the material stops. This angle varies for different materials, but to obtain runouts like those of mudflows they should be in the range of 1º-8º, and never greater than 15º for materials with a low tendency to flow. Using friction angles around 30º almost inhibits mobilization.
The paper also suggests that to simulate mudflows, it is recommended to use the Turbulent-Coulomb formulation for coarse tailings and Bingham formulation if the materials are fine and plastic.
The numerical model considers the variability of the soil characteristics in the initial terrain and tailings as well as how the fluid properties such as density, viscosity, and yield stress change in time and space as the materials flow and interact with the terrain soils and other water bodies.
The application shows the importance of considering an appropriate rheological formulation for the tailings deposit and the dynamic interaction of tailings with their surrounding environment. The paper can be of interest to professionals involved in assessing risk and mitigation measures related to tailings dam breaks.
