A resistência não drenada é um parâmetro geotécnico de grande importância para dimensionamento e avaliação do comportamento de obras sobre solos moles. Essa propriedade é amplamente estudada no âmbito da engenharia geotécnica, com o objetivo de se conhecer melhor suas variações de acordo com outras propriedades físicas e mecânicas dos solos. Este trabalho busca avaliar os resultados da medida da resistência não drenada em diferentes solos artificiais através de ensaios de palheta de laboratório, do cone de queda livre de laboratório e ensaios triaxiais, bem como a relação desse parâmetro com a tensão de pré-adensamento e a plasticidade dos solos. Para tal, foram moldados quatro traços de solos artificiais à base de caulim, com diferentes teores de bentonita, e adensados sob diferentes tensões. Encontraram-se relações entre o aumento da resistência não drenada com ambos os parâmetros avaliados para cada um dos solos e não foram verificados indícios de diferenças estatisticamente significativas entre as medidas médias de cada um dos ensaios realizados para um mesmo solo. PALAVRAS-CHAVE: Resistência não drenada, Solos artificiais, Ensaios de laboratório.ABSTRACT: Offshore and embankments designs are common in engineering practice. For this, an important parameter is the undrained strength of soils, which is vastly studied in order to improve the knowledge of its variability with other physical and mechanical soil properties. This paper aims to provide an evaluation of differences between three laboratory tests: vane test, fall cone test and triaxial UU, as well as evaluate the relationship with plasticity and overburden pressure of soils. In order to that, four kaolin and bentonite mixtures proportions were molded and consolidated at three different loading levels. Were found relations involving these factors variation and the response, also the statistical methods used for evaluation didn't suggest significant differences for the results of each undrained strength measure from laboratory tests realized.
The disposal of iron ore tailings in dry stacks has become increasingly common in Brazil. In these structures, the iron ore tailings are compacted in layers using drum rollers that cause compaction and vibration efforts on the ground. Particle breakage is usually observed in granular materials when subjected to static loads of great magnitude, as can occur depending on the stacking height achieved. However, particle breakage also may occur during the layers’ compaction. This study investigates the breakage behaviour of iron ore tailings simulating load conditions that may occur during dry stacks construction. Two usual iron ore tailings with different amounts of clay size particles, but similar mineralogy (about 77% quartz and 19% iron oxide – the usual composition of iron ore tailings in Brazil) were subject to cyclic oedometer tests. Particle size distribution analyses were performed before and after testing all specimens. Both iron ore tailings, representing typical physical and mineralogical characteristics of the Quadrilátero Ferrífero (southeast Brazil), only suffered particle breakage (Relative Breakage between 0.12 and 0.14 for tailings A and between 0.14 and 0.16 for tailings B) under extremely high pressures (σ’v = 85 MPa) applied by oedometer testing, above those usually found in the field. For usual pressures applied in the field, the frequency of load and number of cycles were of no significance in particle breakage.
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