Ensaios triaxiais em materiais muito moles a baixas tensões de adensamento

Abstract

Anisotropic compression and extension triaxial tests have been carried out on the very soft Sarapuí II clay following NGI procedure, where the specimen is loaded to insitu stresses. Two procedures were adopted: estimating K0 from DMT tests (CAU tests) and using the automated system from the Geocomp apparatus used (CK0U tests). Comparing both types of test, a good agreement was obtained. As the samples depths are small, the values of consolidation stresses and the undrained shear resistances obtained are low and then the unwanted effects (filter, topcap and piston weights, friction on soil-chamber top interface and membrane resistance) become relevant. It was concluded that, even though unwanted effects affect test measurements, they can be properly considered, allowing reliable test results. Undrained shear resistance obtained from triaxial tests was compared to DSS tests, resulting in Su,ext < Su,DSS < Su,comp. A comparação da razão Su,ext/Su,comp versus Ip para argilas de diferentes valores de Ip considerando-se também os dados da presente pesquisa, permitiu verificar-se que o aumento de Ip tende a provocar um aumento de Su,ext/Su,comp apenas até um certo limite, a partir do qual esta razão parece se estabilizar. The analysis of the ratio Su,ext/Su,comp versus Ip for different clays, now including the data from the present research, suggests that there is a threshold of the trend of increasing Su,ext/Su,comp with the increase of Ip. The Skempton parameter A on failure (Af) was determined and compared to literature prediction, and a good agreement was obtained.