Study of the Geomechanical Behavior of a Compacted and Undisturbed Tropical Residual Soil from the Barreiras Formation in Bananeiras, PB

Abstract

The tropical residual soils of the Barreiras Formation, widely distributed along the Brazilian coastal region, exhibit great geotechnical variability. This study aimed to characterize a soil profile from this formation in Bananeiras, PB, evaluating the behavior of the material in its natural and compacted states, with emphasis on the influence of compaction on its mechanical properties. The profile, derived from sandstone, comprises three distinct layers analyzed through grain size distribution, X-ray diffraction (XRD), X-ray fluorescence (XRF), Crumb Test, permeability, suction, Standard Penetration Test (SPT), oedometer compression, direct shear, and triaxial tests. The first layer (AM-01), a sandy clay (CL), exhibited instantaneous collapse and low swelling potential; the second (AM-02), a sandy silt (ML), showed higher strength and expansion; and the third (AM-03), a clay (CL), revealed intermediate behavior. The results confirm the heterogeneity of the Barreiras Formation soils and demonstrate that compaction significantly reduces hydraulic conductivity and volumetric instability, making the material more stable and suitable for geotechnical applications, despite occasional strength losses associated with the breakdown of natural cementation.