Mechanistic Liquefaction Assessment of Mine Tailings

By

Luis Vergaray

Advisor(s):

Dr. Jorge Macedo (CEE)

Committee Members:

Dr. Susan Burns (CEE), Dr. David Frost (CEE), Dr. Paul Mayne (CEE), Dr. Zhigang Peng (EAS)

Date & Time: April 26, 2023 at 11:00 am

Location: (Hybrid) SEB 122 and Zoom: https://gatech.zoom.us/j/99912367893?pwd=bGpXd0lkaUVLOHMxb2pVYllUM1ZkZz09

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.

Keywords: Mine tailings, Static liquefaction, Cylic liquefaction, Critical state, Spatial 
variability