Caracterização, compressibilidade e colapsibilidade de um perfil de solo tropical não saturado
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Data
2021-10-28
Autores
Valverde, Diego Augusto
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Universidade Estadual Paulista (Unesp)
Resumo
Essa pesquisa buscou compreender o comportamento compressível ao longo de um perfil de solo arenoso, não saturado, por meio da caracterização em nível de detalhe e dos parâmetros de compressibilidade e de colapsibilidade. Foram realizados ensaios de caracterização convencionais, adsorção de azul de metileno (CTC), difração de raios-x (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia por energia dispersiva (EDS) em amostras deformadas coletadas ao longo do perfil. Ensaios edométricos convencionais e com sucção controlada também foram realizados em amostras indeformadas coletadas ao longo da profundidade até 16 m, a fim de complementar ensaios já realizados. O solo investigado possui estrutura microagregada oriunda da ação cimentante de sesquióxidos que aderem as partículas mais finas, fazendo com que se comportem como siltes. A compressibilidade do solo foi decrescente com a profundidade e é dependente do efeito da condição não saturada, da forma e tamanho das partículas, macro e microestrutura, confinamento e gênese do solo. Empregaram-se diferentes critérios para a identificação de solos colapsíveis. O critério expedito identificou o comportamento colapsível até cerca de 9m de profundidade. Segundo o outro critério, o solo é verdadeiramente ou condicionalmente colapsível até os 13m de profundidade. Já, o critério baseado nos resultados dos ensaios edométricos duplos, indicam ocorrência de colapso até cerca de 7m de profundidade para os níveis de tensão confinante e de sucção de campo. Observou-se que os valores de módulos de deformabilidade em compressão confinada (Md) aumentaram com as tensões verticais, independente da sucção e da profundidade. Os valores desse módulo (Md) apresentaram boa concordância com aqueles determinados pelo ensaio de dilatômetro plano (MDMT), desde que sejam feitas considerações quanto aos níveis de sucção de campo e ajustes nas correlações.
This research sought to understand the compressible behavior along an unsaturated, sandy soil profile through detailed characterization and from the compressibility and collapsibility parameters. Conventional characterization, methylene blue adsorption (CTC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) tests were performed on disturbed samples collected along the soil profile. Conventional and controlled suction oedometer tests were also performed on undisturbed samples collected along the up to 16 m, to complement tests already carried out. The soil investigated has a microaggregate structure due to the cementing from sesquioxides that adhere to the finest particles, making them behave like silts. Soil compressibility decreased with depth and was shown to be dependent on the effect of the unsaturated condition, particle shape and size, macro and microstructure, confinement, and soil genesis. Different criteria were used for the identify collapsible soils. The expedited criterion identified the collapsible behavior up to about 9m depth. According to the other criterion the soil is truly or conditionally collapsible up to 13m depth. On the other hand, the criterion based on the results of the double oedometer tests indicates collapse occurrence up to about 7m depth for the confining stress and in situ and soil suction. It was observed that the values of the constrained modulus (Md) increased with vertical stresses, independent of the suction and depth. The values of this modulus (Md) showed good agreement with those determined by the flat dilatometer test (MDMT), once considerations are given to in situ suction levels and adjustments are made to the correlations
This research sought to understand the compressible behavior along an unsaturated, sandy soil profile through detailed characterization and from the compressibility and collapsibility parameters. Conventional characterization, methylene blue adsorption (CTC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) tests were performed on disturbed samples collected along the soil profile. Conventional and controlled suction oedometer tests were also performed on undisturbed samples collected along the up to 16 m, to complement tests already carried out. The soil investigated has a microaggregate structure due to the cementing from sesquioxides that adhere to the finest particles, making them behave like silts. Soil compressibility decreased with depth and was shown to be dependent on the effect of the unsaturated condition, particle shape and size, macro and microstructure, confinement, and soil genesis. Different criteria were used for the identify collapsible soils. The expedited criterion identified the collapsible behavior up to about 9m depth. According to the other criterion the soil is truly or conditionally collapsible up to 13m depth. On the other hand, the criterion based on the results of the double oedometer tests indicates collapse occurrence up to about 7m depth for the confining stress and in situ and soil suction. It was observed that the values of the constrained modulus (Md) increased with vertical stresses, independent of the suction and depth. The values of this modulus (Md) showed good agreement with those determined by the flat dilatometer test (MDMT), once considerations are given to in situ suction levels and adjustments are made to the correlations
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Palavras-chave
Ensaios edométricos, Solos não saturados, Solos tropicais, Compressibilidade, Colapsibilidade, Laboratory tests, Oedometer tests, In situ tests, Unsaturated soils, Tropical soils, Compressibility, Collapsibility