Cartwright, Abigail;
(2022)
Investigating cyclic liquefaction in transitional tailings.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The Fundão and Brumadinho dam disasters have focussed attention on the stability of tailings dams, although in fact there have been around 250 tailings dam incidents in the last century. In recent years it has been identified that many natural soils of complex mineralogy and/or mixed grading have modes of behaviour that differ from conventional soil mechanics in that the effects of the initial void ratio at their deposition cannot be erased by loading at engineering stress and strain levels. The normal compression lines and critical state lines that they reach in terms of void ratio are therefore not unique but depend strongly on this initial state. From their origins as crushed rock, it may be expected that the “transitional” behaviour would occur in tailings, but it has often been overlooked as tests on samples of different initial void ratios required to identify this behaviour are rarely carried out. This thesis describes laboratory triaxial and oedometer tests on tailings specifically designed to investigate transitional behaviour highlighting how the strength is dependent on the volume at deposition. The data show how the normal compression and critical state lines move in the void ratio – stress space depending on the initial density and the strong implications for cyclic liquefaction are discussed along with the implications for the method of placement for dam stability. Undrained cyclic tests were carried out on a mineral sand tailings from Australia. Data for a more conventionally behaved tailings, an iron tailings from China, were also reanalysed. The mineral sand tailings was found to be highly transitional and cyclic tests concluded that the initial specific volume did not make a significant difference to the mechanical behaviour and initial specific volume was found to be much less important than the cyclic stress ratio, CSR, and the initial mean effective stress.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Investigating cyclic liquefaction in transitional tailings |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10152682 |
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