Mechanistic Liquefaction Assessment of Mine Tailings
Author(s)
Vergaray Astupina, Luis Fernando
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Abstract
During the last decade, tailings storage facility (TSF) failures have caused unprecedented environmental consequences and loss of human lives worldwide (e.g., Brazil, Australia, Canada, and South Africa). A failure in the United States, similar to other recent ones, may cause dramatic damage to the environment, state economies, and local communities. The static liquefaction phenomenon has been prevalent in several of the recent TSF failures, e.g., the 2015 Fundao failure, where the stored mine tailings liquefied. Cyclic liquefaction has also historically affected TSFs. A prime example is the 2010 Las Palmas failure after the Mw 8.8 Maule earthquake in Chile, where the stored tailings suffered flow liquefaction. Assessing the liquefaction phenomenon in mine tailings imposes several fundamental challenges as tailings are man-made young materials with angular grains, often lower proportions of quartz, and significant compressibility. Thus, standard geotechnical methods and correlations should not be taken as applicable to tailings without detailed consideration of these factors. Moreover, there is a disparity in how static and cyclic liquefaction are assessed. Often the former considers mechanical parameters, whereas the latter relies on empirical methods developed for natural soils. In this context, this thesis contributes to advancing the understanding of the mechanical properties of mine tailings for liquefaction assessments considering static and cyclic solicitations. In addition, it proposes changing the paradigms in assessing cyclic liquefaction by bringing mechanics. Towards these goals, (1) trends in mechanical parameters for assessing static liquefaction are discussed, (2) the static liquefaction phenomenon is assessed under prevailing drained paths that have shown relevance on case histories, (3) insights gained from interpreting liquefaction-oriented laboratory tests considering contrasting mine tailings gradations are shared, (4) the role of spatial variability in deposited tailings is showcased, (5) the robustness of a mechanistic framework for assessing cyclic liquefaction is assessed, and (6) its application to a case history with materials with contrasting properties is showcased.
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Date
2023-07-07
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Dissertation