A Realistic Technique to Obtain the Surface Contours of Conventional, Thickened and Paste Tailings Storage Facilities

Abstract

Understanding the surface fluctuations of a dry stack, paste, thickened and conventional tailings storage facility can help manage the day to day tailings disposal operations. This in turn helps to increase the safety of the facility and reduce the hazards associated with a failure. The majority of conventional tailings failures arise from poor water management, most notably loss of freeboard. Controlling the geometry of the supernatant pond and the freeboard of a conventional tailings facility are perhaps the fundamental parameters influencing embankment stability. Although dry stack, paste and thickened tailings facilities don’t have to control supernatant water as stringently, there is a need to control the geometrical properties of the facility. Calculating the contours of a tailings facility accurately can help give a better insight into how the facility is performing and how it will perform in the future. This is perhaps better presented by highlighting the advantages to attaining elevation data: Conventional surface impoundments: Areas that are susceptible to loss of freeboard can be determined. The area and volume of the supernatant pond can be calculated accurately. The available volume of tailings that can be stored at current embankment elevations can be determined. Depth of water around decant towers and barges can be determined. The expected geometry of the supernatant pond if there is an elevation change (e.g. storm, decant system failure) can be calculated. The flow paths from individual spigots can be determined. Beach widths and angles can be measured. Variable consolidation rates can be assessed. Areas of internal erosion or foundation settlement (e.g. piping, sink hole development) can be identified. Paste2006–R.J.Jewell,S.Lawson,P.Newman(eds) ©2006AustralianCentreforGeomechanics,Perth,ISBN0-9756756-5-6 Paste2006,Limerick,Ireland 221 Dry stack, paste, thickened impoundments: The area and volume of the stacked material can be calculated. The likely flow paths of the tailings discharging from the spigots can be identified. Calculation of the likely zoning timescales and covering of desiccated areas is possible. The slope angles of the deposit can be measured. The areas around the perimeter where the bleed water will collect can be identified. It is important to have a high accuracy of elevation data as the majority of tailings facilities cover large areas which can cause a significant error to water management calculations. This is particularly true for conventional tailings facilities where the beach angles are shallow and there is a significant distance between the discharge points and the decant facility. Determining elevation data of a tailings facility can be achieved by a variety of methods. This paper summarises various methods of obtaining elevation data of the surface of a tailings facility quickly, easily, accurately and in a cost effective way. The idea behind this research is to establish highly accurate data to allow 3D models to be generated which can be modelled with GIS software. These models will be discussed and a few examples given to demonstrate how knowing elevation data can help to improve the management of a tailings storage facility. One of the most notable outcomes of these models will be the ability to predict supernatant pond geometry, the flow paths and accumulations from multiple discharge points.