The growing trends in tailings management are to eliminate ponded water on top of tailings and to thicken tailings to conserve water and minimise the amount of water that has to be managed. There are various degrees of thickening ranging from a high density, non-segregated slurry, to a paste and filtered tailings.Thickened tailings, with a consistency of a high density, non-segregated slurry or a paste can be safely deposited at slopes between 2-10% in thin layers that allow for desiccation with relatively small containment dams at the toe. However, stability is a concern, especially for large tailings deposits because the deposited properties can not accurately be predicted beforehand. Empirical relationships have not been developed because there is insufficient field data. This paper discusses the stability of thickened tailings stacks (slopes) in both the short-term during operation and long-term in the closure mode. The authors have developed an innovative design methodology based on critical state soil mechanics fundamentals that can predict the stability of thickened tailings slopes and the change in the factor of safety with time. This tool can also be used to carry out sensitivity analyses for different operational conditions and different tailings properties so that deposition strategies can be optimised. Thin layer deposition and desiccation are necessary to ensure the stability of these slopes. A feature of the method is that the deviations from the design assumptions are evident shortly after deposition commences allowing time to implement changes.

This concept will address the structural problem of failure due to cracks which are either hidden, in the presence of corrosion, due to stress-corrosion cracking, cracking in multi-layer structures, or cracks in fastener holes in multilayer structures. It will also provide useful information with regard to Usage monitoring/data recording.

The results of laboratory and in situ testing and test blasting, the observations made on a test embankment, and a description of actual construction practice associated with engineering studies for the management of uranium mill tailings at Elliot Lake, Ontario are presented. Relative density values inferred from standard penetration tests and cone penetrometer tests are shown to be inconsistent with relative density values determined from maximum and minimum void ratios. Some of the data contradicts existing correlations.The compressibility of in situ saturated tailings is presented in graphical form in terms of void ratio, vertical effective stress, and mean grain size. Hydraulic conductivity is shown to range over many orders of magnitude, depending on the void ratio. The observations on an instrumented test embankment are used to explain the appropriate selection of geotechnical parameters that gave good agreement between back-calculated and observed settlements. One-dimensional consolidation theory was found to be valid for the embankment case. It is necessary to account for changes in soil properties that occur during the consolidation process in order to obtain a good fit between back-calculated and observed settlements. The successful use of tailings sand for embankment construction is described. On the basis of normalized standard penetration resistance values, it is concluded that localized zones of saturated tailings may be prone to liquefaction under predicted earthquake loadings. Key words: uranium tailings, geotechnical parameters, relative density, test embankment, liquefaction.

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This concept will address the structural problem of failure due to cracks which are either hidden, in the presence of corrosion, due to stress-corrosion cracking, cracking in multi-layer structures, or cracks in fastener holes in multilayer structures. It will also provide useful information with regard to Usage monitoring/data recording.