Authors: Seddon, KD; Dillon, MJ


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Seddon, KD & Dillon, MJ 2009, 'The Effect of Evaporation on Strength and the Stability of Thickened Tailings Beach Slopes', in R Jewell, AB Fourie, S Barrera & J Wiertz (eds), Paste 2009: Proceedings of the Twelfth International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 261-269,

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At the time a layer of tailings slurry comes to rest on the surface of a tailings beach and settles, it has very low shear strength. Before additional layers of tailings are placed over this layer, the strength must increase, or the driving forces of the accumulated tailings will exceed the shear strength, and mass instability will result. The undrained shear strength of tailings in a beach is a function of the moisture content and density of the tailings. Test methods to establish this relationship are discussed and compared. The effects of surface area and evaporative drying can be combined to analyse the final moisture content, density and shear strength achieved on a beach. The theoretical results are compared to the results of field trials. The influence of climate and tailings type can be important. Under critical combinations of climate, tailings and placement rate, very low strength layers may remain in the tailings at depth. In the first instance, a static type failure may result (i.e. a failure without any triggering mechanism such as an earthquake). A possible example of this type of failure is proposed.

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