ABSTRACT
Natural soils consist of relatively loose assemblages of discrete mineral and organic particles of various shapes and sizes. Although it is convenient to simplify them as continuous media for the purposes of analysis, properties at particle level may ultimately control their engineering behavior. Gold tailings can be considered a “man-made” soil with properties between those of sand and clay. The soil forming processes on a typical tailings impoundment lead to a highly layered vertical profile, with coarse layers (“sands”) alternating with fine layers (“slimes”). In addition to the vertical layering, the horizontal spatial distribution is also highly variable and dependent on the properties of the tailings slurry and the depositional program. In South Africa gold tailings impoundments are almost always constructed using the daywall-nightpan paddock system. In designing a tailings impoundment it is assumed that the more competent coarser material will be deposited near the embankment and the finer material in the central part of the impoundment. This paper will illustrate that although there is a general trend of finer composition towards the central area, a significant amount of fines are trapped in the day-wall and settle on the beach. The composition, i.e. mineralogy and particle properties of both fine and coarse materials has been investigated using electron microscope and x-ray techniques, and is described.
