Resistência e compressibilidade de solos da Formação Barreiras da região de Natal/RN

Abstract

Most of the infrastructure and cities present in the region of the state of Rio Grande do Norte – (RN) is seated on the geological unit called Barreiras Formation. This coastal area show, in its territory, geological formations that are due to the seasonal moisture of its weather and erosive action, called Tropical Residual soils, or Lateritic. The climatic behavior of the region implies in the desiccation of the soil profile, which have direct influence in the parameters of strength, compressibility and permeability of the soil. To determine the behavior of lateritic soils in the different conditions in which it may presents (saturated or unsaturated) presents itself as a necessity, as means to evaluate the safety of the city’s infrastructure seated over these formations. The objective of this study is the geotechnical characterization of Barreiras Formation samples, and evaluation of the strength and compressibility parameters obtained. To that end, 14 non deformed samples of soil were collected from the East and North zones of the city of Natal/RN, in lands next to the Potengi River area. The samples have gone through granulometric analysis, direct shear tests in flooded and natural conditions of the soil, and oedometer tests with flooding in the 100 kPa stress. The direct shear tests were executed using confining stress of 50; 100; 200 and 400 kPa, while in the oedometer tests the samples were submitted to vertical stress of 12,5; 25; 50; 100; 200; 400 and 800 kPa. As results, it was noted that around 70% of the samples analyzed were characterized as clayey sands, and that in the non-flooded tests were obtained values of cohesion as high as 200 kPa, but the flooding of the sample leads to expressive decline of this parameter, and variation of the friction angle by 20%. The Oedometer tests showed to the occurrence of isolated collapsing behavior in one of the tested samples, with a vertical strain of 9.8%, and the rest of the samples showing maximum strain of 1.8%, with void ratios going from 0.375 to 0.560, compression index of 0.033 to 0.392, and a recompression index of 0.014 to 0.02.