Geotechnical properties of some kaolinite-rich Brazilian Vertisols

Abstract

Vertisols presenting kaolinite codominance or prevalence were already reported in several countries worldwide. However, the literature has few studies focused on investigating the influence of this clay mineral in soil geotechnical behavior. This study aimed to carry out the characterization of Vertisols in Bahia State, Brazil, to understand the influence of physical, chemical, and mineralogical properties on their geotechnical behavior, as these soils have high natural fertility and have been used for agricultural activity, but with great risk due to their physical and geotechnical properties. Six Vertisols were selected, three located in Juazeiro County (Semiarid region) and the other three in Recôncavo region. Geotechnical characterization of selected soils was carried out in their respective diagnostic horizons by determining properties such as granulometric curve, Atterberg limits, clay activity, linear expansion coefficient, compaction capacity, cohesion (c), and internal friction angle (ϕ) of saturated soils. Soil expansion potential was associated with expansive clay contents and clay content in each soil sample. The best soil compaction efficiency was observed for kaolinitic Vertisol, which presented greater void ratio reduction and higher density due to moisture increase. In addition, c increased as kaolinite content also increased and decreased as clay content increased in soils presenting similar mineralogy. On the other hand, ϕ was influenced mainly by granulometry since higher sand and gravel levels enabled higher ϕ, regardless of clay type.