This paper discusses the issue of the true reliability of a beach slope prediction method. Beach profiles have been predicted for five sites where there is reasonable information available regarding the operating variables that influence slope. Data derived from operating records show significant variability in two of the main controlling parameters: throughput (flow rate) and solids concentration (rheology or flow resistance). A combination of these variables has been used to calculate predicted beach slopes over the top, middle and lower thirds of the tailings beaches studied. Reasonable agreement between predicted and observed profiles has been obtained for both the overall slopes, and the measured slope concavity.

No abstract

Modelling of a tailings beach using a time series of thickener output (flow rate and solids concentration) was first reported by Fitton et al. (2007). Seddon and Fitton (2011) presented statistical data on the performance of thickeners, and showed that the observed concave shape in tailings beaches could be adequately explained by this variability. They then proposed a stochastic method for the generalised modelling of tailings beaches. The aim of this paper is to demonstrate the application and results obtained by the use of this method. This paper shows how thickener performance statistics in the form of frequency functions for variations in (a) underflow solids concentration; and (b) mass flow rate, can be combined with a set of rheology results to develop a predictive beach slope distribution. Data developed from this distribution are then used as an input to a deposition modelling program. The developed beach profile is presented for a typical case.

The operational fluctuations of tailings thickeners have the potential to cause significant impacts on the tailings transport system and the tailings deposition at a tailings storage facility (TSF). The statistical analysis of actual recorded data of underflow solids concentration and flowrate of different thickeners is presented in this paper. The collected data are from the operation of four different mines; one Zinc-lead, two Copper and one Gold mine. The variability in these two important parameters can be related to process fluctuations, design or construction defects including instrumentation and controls, the variability in mine orebody during the life of the project or operation of the thickener. The analysis of the data shows that the actual performance of the thickener can be significantly different from what is usually considered at the design stage. An example is presented to show the impacts of thickener performance variability on tailings transport system and thickened tailings beach slope quantitatively.

A series of tilting (variable slope) flume tests were undertaken at the pilot plant facility at Chuquicamata copper mine in northern Chile to study the achievable tailings beach slope for different tailings solids concentrations and flowrates. The pilot plant facility was part of a prefeasibility study into upgrading the existing conventional tailings disposal facility, to a thickened tailings disposal scheme. The tilting flume facility was included into the pilot plant trial to produce reliable data for verification of theoretical beach slope prediction models. The tests were conducted on existing tailings from the Chuquicamata plant. A pilot size (2.5 m diameter) thickener was used to thicken the slurry to higher solids concentration before feeding the tilting flume. A range of different slurry flowrates (ranging from 5.5 to 18 L/s) and solids concentrations (ranging from 56.5 to 72.5%) were tested. The testing methodology, the test results and analysis, are discussed in this paper. The actual measured beach slope (based on hydrodynamics of channel flow theory) for each flowrate and slurry solids concentration are also presented.