Integrating Site Conditions, Rate of Rise and Deposition Sequence to Beach Slope Estimations for High Thickened Tailings

Abstract

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.