Análise do comportamento geotécnico de seis solos representativos de unidades pedológicas da região de Mossoró – RN.

Abstract

Expansive and collapsible soils, common in semi-arid regions, are unsaturated soils that exhibit significant volumetric changes with moisture variation. This characteristic makes them problematic for civil engineering, as they can compromise the stability of buildings and infrastructure due to unfavorable geotechnical behavior resulting from local climatic conditions. In this context, the present study evaluates the expansion and collapse potential of six soils from the municipality of Mossoró. The methodology involved the collection of disturbed and undisturbed samples, the performance of laboratory tests—especially physical, chemical, and mineralogical characterization, as well as expansion and collapse tests—and field investigations. Most of the analyzed samples belong to the Jandaíra Formation, the main lithostratigraphic unit of the Potiguar Sedimentary Basin. The majority of samples were classified as clayey sand, with some showing significant percentages of fine particles, while others revealed a considerable presence of gravel. Regarding soil mineralogy, some samples showed the presence of 2:1 clay minerals, belonging to the smectite group, which are associated with a higher expansion potential. The expansion tests conducted on both disturbed and undisturbed samples showed significant variability in the expansive behavior of the analyzed soils. Laboratory data revealed that greater volumetric deformations were not always associated with higher stresses required to recompress the samples, highlighting the complexity of the expansion phenomenon. Analyses of vertical strain trajectories indicated that, in soils with low expansion potential, there was no significant difference between the expansion stresses obtained using Methods A and C, as described in ASTM D4546-21. In turn, the collapse indices of the analyzed soils ranged from slight to moderately severe, and in some cases, even when the index did not exceed the conventional threshold of 2%, significant deformation over time was observed, indicating relevant instability. The results reinforce the importance of thorough geotechnical characterization for accurately predicting the behavior of the studied soils, contributing to the safe planning of construction projects in semi-arid regions such as Mossoró.