Liquefaction Potential of Surface Deposits of High-Density Thickened Tailings

Fourie, Andries

doi:10.36487/acg_repo/663_10

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…Specimen preparation techniques used in the current study were consistent with those of Reid & Fourie (2014) previously outlined. As the constituents of the slurry are commercially available standard soils it was possible to closely reproduce the mixture previously use in the 2011-2014 period.…”

Section: Sample Preparationmentioning

confidence: 85%

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

Reid¹,

Tiwari²,

Fourie³

2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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Polymer treatment (PT) of tailings has been observed experimentally and in physical models, resulting, in some cases, in changes to geotechnical properties including: (i) higher hydraulic conductivity, (ii) lower density at a particular vertical effective stress, (iii) a change to the critical state line (CSL), and (iv) different penetrometer response when at the same in situ state. The different CSLs observed could be theorised to converge at sufficiently high strain once the PT fabric had broken down through shearing. However, the available penetrometer test results in controlled centrifuge experiments do not support the suggestion of converging CSLs, with drastically different cone penetration test (CPT) resistance seen in PT clayey silt of importance as the CPT represents a large strain measure. To further investigate PT effects on shearing, a series of multi-stage direct simple shear and constant volume ring shear tests was carried out to investigate the large strain response of untreated (UT) and PT specimens. The tests showed consistently higher, or similar, large strain strengths from PT specimens despite their lower consolidated densities. This result is generally consistent with previous observations of an increase to CSL elevation from PT.

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Section: Sample Preparationmentioning

confidence: 85%

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

Reid¹,

Tiwari²,

Fourie³

2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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“…In the literature, there is paucity of research on the stability of non-segregated tailings stacks. Previous studies show that the stability of thickened tailings stacks is most critical when tailings liquefy under seismic conditions (Poulos et al, 1985;McMahon et al, 1996;Seddon et al, 1999;Fourie, 2006;Barrera and Riveros, 2006;Seddon, 2007) and efforts were made to predict the safety margins. However, the stability of tailings stacks under both shortterm and long-term conditions has not been fully addressed.…”

Section: Figure 1 Variation Of Tailings Depositional Slope With Taili...mentioning

confidence: 99%

Stability of Large Thickened, Non-Segregated Tailings Slopes

Li¹,

Been²,

Ritchie³

et al. 2009

Proceedings of the Twelfth International Seminar on Paste and Thickened Tailings

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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.

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Physical, chemical and mineralogical characterisation of hydraulically disposed fine coal ash from SASOL Synfuels

Mahlaba

Kearsley

Kruger³

2011

Fuel

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a b s t r a c tCoal serves as the primary energy source in most parts of the world. It is a fact that coal combustion yields enormous quantities of fly ash some of which are either hydraulically placed or dry dumped. The current study attempts to provide a comprehensive characterisation of a disused alkaline fine coal ash dam (FCAD) towards assessing environmental impact, rehabilitation and utilisation potential. Fine coal ash refers to a combination of approximately 83% power station fly ash and 17% gasification and bottom ash fines (particles <250 lm) at SASOL Synfuels. The hydration products found in Weathered Fine Coal Ash (WFCA) using X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) are analcime, calcite, C-S-H gel, ettringite, hydrated gehlenite (Strätlingite), magnetite, periclase, pyrrhotite and sillimanite. High resolution Scanning Electron Microscope (SEM) results provide additional proof that hydration products are present in WFCA. No indication of appreciable leaching was given by X-ray Fluorescence (XRF) results except calcium and silicon. Thus evidence exists that pollutants from saline brines are immobilised in WFCA and an insight of reaction kinetics was obtained. High content of amorphous phase and lack of alteration in some geotechnical properties suggest that WFCA can be reutilised with lime addition to increase alkalinity and activate pozzolanic reactions.

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Liquefaction Potential of Surface Deposits of High-Density Thickened Tailings

Cited by 3 publications

References 8 publications

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

Stability of Large Thickened, Non-Segregated Tailings Slopes

Physical, chemical and mineralogical characterisation of hydraulically disposed fine coal ash from SASOL Synfuels

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