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.
The application of highly thickened tailings technologies is rapidly increasing due to the perceived benefits with respect to reduction of environmental impacts, water savings and potential reductions in dam size and footprint impoundment. Evaluation of this potential benefits requires that during early design stages an understanding is developed for the range of feasible beach slopes to be achieved during deposition. A comprehensive evaluation of the whole range of factors that influence the beach formation process is paramount to ensure that expected performance during design stages is met throughout operations. This paper presents an integral approach for beach slope estimation, considering a broader range of aspects affecting the beach formation process than those commonly used in current models (rheology and discharge rate of the deposited tailings). The additional aspects considered by this approach are site conditions (site morphology and climate), the rate of rise of the tailings impounded (the relationship between the tailings production rate and the available area for tailings spreading) and the deposition sequence (the configuration of the deposition system and its operation, e.g. thin layer deposition with drying cycles).The approach is supported by a beach slope model based on 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 sub-aerial disposal. This dimensionless parameter provides a closed expression for estimating tailings beach slopes based on rheological properties and discharge rates, but with the integration of site conditions, rate of rise and deposition sequence.High thickened tailings management facility (TMF) design is well supported by this approach, providing key input as the configuration of the distribution system and the minimum area required to achieve expected performance with respect to desired beach slope, density, degree of saturation and strength.
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