Effects of Hydraulic Gradient Variation on the Structure and Strength of a Compacted Tropical Soil

Abstract

Tropical soils have been extensively studied to evaluate the technical feasibility of their application in hydraulic earthworks such as compacted clay barriers in landfills. In these earthworks, the water flow in the porous medium generates percolation forces that can promote structural changes in the soil, with possible deleterious repercussions on its mechanical and hydraulic properties. In this context and considering the geotechnical peculiarities of tropical soils, this research aimed to characterize the influence of the hydraulic gradient used in column percolation tests on the structure of a compacted tropical soil and, therefore, on its shear strength. Compacted test specimens were subjected to water percolation tests and then to direct shear tests. Thin sections were removed from the compacted layers for micromorphological analysis. The results showed that, statistically, at 5 % probability level, no significant variation in the overall mean shear strength and in the micromorphological features was found as a function of the applied hydraulic gradients. In general, the non-statistically significant change in soil structure also justifies the lack of significant variability on shear strength. The research highlights the importance of micromorphological analysis supported by statistics in understanding the structural aspects of compacted soils responsible for their engineering behaviors.