The effect of tamping conditions on undrained shear strengths of a non-plastic sandy silt tailings

Abstract

A series of direct simple shear (DSS) tests were carried out on a non-plastic sandy silt lead−zinc−silver tailings to develop a relationship between undrained shearing behaviour and density for contractive states. The critical state line was also obtained through triaxial compression tests to enable the DSS tests to be viewed in a critical state framework and allow comparison with in situ testing. It was found that the gravimetric water content (GWC) used to tamp the specimens had a significant effect on the resulting undrained strengths when attempting to achieve dense states — with higher GWC giving lower strength at a given density than a lower GWC. Intact and slurry deposited (SD) samples were also tested to access denser states without inducing tamping-related stresses. These showed a more consistent trend with the loose-tamped specimens, and with other data from the literature. Plausible explanations as to the causes of the increased strength of dense-tamped samples were obtained through estimating potential preconsolidation stresses and “locked in” horizontal stresses that may occur from dense tamping. The importance of these observations on the development of density−strength profiles in engineering practice was outlined.

Análise da variabilidade inerente através de em ensaios de piezocone: aplicação a resíduos de mineração

“…Como as barragens de rejeitos frequentemente são compostas por materiais não coesivos (areia siltosa, misturas arenosas), a obtenção de amostras indeformadas é difícil. Também, sabe-se que a reconstituição de amostras para ensaios de laboratório resulta em diferentes estruturas de acordo com os diferentes métodos de moldagem, que podem resultar em diferentes características de tensão e deformação, logo de comportamento (Carraro e Prezzi, 2007;Reid et al, 2021). Contribuciones a Las Ciencias Sociales, São José dos Pinhais, v.16, n.11, p. 28547-28564, 2023 Para a caracterização in situ de rejeitos, o ensaio de piezocone (CPTu) é o instrumento de teste mais amplamente utilizado (Ayala et al, 2022).…”