Tailings beach slopes as a dimensionless parameter of non-Newtonian flows

摘要

The application of highly thickened tailings technologies is rapidly increasing due to the perceived benefits with respect to reduction of environmental impacts, water saving and potential reductions in dam size and impoundment footprint. Evaluation of these potential benefits requires that during design stages an understanding is developed of the range of feasible beach slopes to be achieved during deposition. A comprehensive evaluation of the operational factors influencing the beach formation process is paramount to ensure that expected performance during design stages is met throughout operations. This paper presents the derivation of a dimensionless parameter for non-Newtonian flows, associated with sheet flows on an inclined plane, which directly relates to the tailings beach slope expected to be formed due to subaerial disposal. This dimensionless parameter provides a closed expression for estimating tailings beach slopes based on rheological properties and discharge rates considering that sheet flow mechanisms occur. Conditions for sheet flow occurrence, such as level of further dewatering of the beach after deposition, active discharge times and geometry of active discharge areas, can be derived within this formulation. The dimensionless parameter and conditions found to promote sheet flow also allow to address the advantages and limitations of different discharge operation strategies, such as operating the tailings facility by sectors (allowing drying cycles) of varying geometries. Evaluation of this approach in the light of case histories is presented. Finally, discussion on how to evaluate the potential of having concave tailings beach profiles within this formulation is provided.