Avaliação da suscetibilidade à liquefação com base em ensaios CPTu, com aplicação à Barragem de Fundão, Mariana (MG)

Abstract

The phenomenon of liquefaction occurs abruptly in natural soils or artificially constructed structures, such as tailings containment dams. Therefore, a well-elaborated design of dams becomes essential, to guarantee their safety, to protect lives, the environment, and the constructions in the vicinity. Lately, the safety of dams has been reviewed, due to the frequent failures. The analysis of the liquefaction susceptibility is of paramount importance in unconsolidated sandy soil structures with contractile potential. In Brazil, the study of static liquefaction has been a priority, due to the geotechnical characteristics of granular tailings. There are several methods, in the literature, to evaluate soil liquefaction potential. However, the cone penetration test, with pore pressure measurements (CPTu) is the most used. The test estimates different geotechnical properties, including the state parameter (ψ). The present work aims to evaluate and compare the CPTu methodologies proposed by Been et al. (1987), Been et al. (1988), Plewes et al. (1992), Shuttle and Cunning (2007), Torre-Cruz (2021), Robertson (2010), Robertson (2016) and Robertson (2022). Five CPTu records (F01, F02, F03, F04, and F05) from the Fundão tailings dam, in Mariana (MG), were used. The profiles were extracted from Morgenstern et al.’(2016) report The study showed significant differences in predicting the liquefaction potential and evidenced the complexity of obtaining reliable results. Besides the intrinsic uncertainties associated with the formulation of the methods, the main differences were related to the slope of the critical state line (λ10). It is therefore recommended that, in geotechnical practice, more than one method is used before decision-making.