A influência da mineralogia secundária no comportamento mecânico de um solo residual granítico no semiárido brasileiro

The influence of secondary mineralogy on the mechanical behavior of a granitic residual soil in the semiarid region of Brazil

Abstract

Abstract: The external geological processes that form soils play a crucial role in their behavior. In the specific case of residual soils, cementation rather than stress history plays a fundamental role in their mechanical behavior. The aim of this work is to assess the influence of the mineralogy present in a granite alteration profile in the Brazilian semi-arid region on its mechanical behavior, specifically in terms of direct shear. The study was carried out on the topsoil of granitic rocks. Disturbed and undisturbed samples were taken at three points. XRD analyses were carried out on the sand and fines fractions for mineralogical characterization and XRF analyses for chemical characterization of the points studied. Geotechnical characterization tests included granulometric analysis and consistency limits. Direct shear tests were carried out to study the mechanical behavior. The results showed that the mineralogical composition, soil structure and the cementing role of iron minerals are the main factors causing the mechanical behavior of the soil studied. Local variations in the drainage capacity and the degree of soil weathering explain the presence of secondary minerals and the differential mechanical behavior of the samples studied.