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CyGS Virtual Presentation with Mike Jefferies: Analysis of Static Liquefaction with Plaxis - 1974 Tar Island Slump
Finite element analyses using critical state theory proved necessary to understand the development of static liquefaction during three recent large tailings dam failures at Fundao, Cadia, and Brumadinho. However, the complexity of these events prevents these analyses from being viewed as a complete validation of the methodology. Here we evaluate a far simpler case of static liquefaction: the 1974 Tar Island slump, which involved a rapid drop of 5 m during construction of a 12.5 m high upstream raise over loose tailings. While not a dam stability issue, the event has the attraction of being load-induced, with simple geometry, and with known material properties and in-situ state. The analyses were carried out with commercial software (PLAXIS) and use critical state theory with largely familiar soil properties measured by standard methods. The computed liquefaction develops from a prior drained condition, with essentially no precursors, before propagating rapidly undrained – there are similarities to the video record at Brumadinho, and an animation will be shown to illustrate this. As a related historical note, the theory and methodology were originally developed in Calgary 1982-1989 by Gulf Canada Resources albeit strongly based on work by the US Corps of Engineers.

Nov 17, 2021 12:00 PM in Edmonton

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