Assessment of the potential for liquefaction using CPTu in the tailings dam I – Feijão

Abstract

In Brazil in 2019, the failure of the tailings dam I - Feijão costed a total of 7 billion dollars in civil and environmental reparation. The report of the expert panel that evaluated the failure of dam I concluded that the failure was due to static liquefaction, which is one of the most common dam failures in the world. However, the identification of the liquefaction potential has challenges such as identifying the behavior of the tailings (contractive and dilative behavior) and extracting undisturbed samples for sophisticated laboratory tests. CPTu is a fast and reliable field test, and, through empirical relationships, the liquefaction potential of soil can be estimated using the state parameter (ѱ). The objective of this article is to present the results of piezocone (CPTu) in the different in situ geotechnical campaigns in Feijão Dam with focus on the state parameter (ѱ) data used to determine the liquefaction potential. The methodology used herein is that ѱ > -0.05 means contractive behavior or high change of potential for liquefaction. The results show that the CPTu tests in dam I - Feijão showed that there was high liquefaction potential during the geotechnical campaigns (2005, 2016, and 2018) by using this procedure.