Geotechnical Characterization and Failure Mechanism of Landslide in Granite Residual Soil

This paper describes the geological-geotechnical study of the occurrence of a mass movement on a hillside in the municipality of Camaragibe, Pernambuco state, Brazil. Comprehensive onsite geotechnical investigation was performed involving borings, collection of deformed and undisturbed samples, moisture profiles, hydraulic conductivity tests (Guelph permeameter), and study of wastewater disposal. Laboratory tests were performed, including chemical, mineralogical and physical characterization, permeability (triflex), suction studies, oedometer, direct, suction-controlled, multiple reversal, and ring shear tests; instrumentation also involved the use of Casagrande and maximum piezometers, water level gauges, slope indicators, and a pluviometer. The data obtained in the laboratory and on site enabled characterization of the materials involved in the landslide (Barreiras Formation and granite residual soil) and understanding of the mechanism, its stability analysis at the failure stages, and reactivation. It is cited as having predisposing factors to instability, namely geology, anthropic action, and relief. Rainfall was indicated as the primary triggering factor. At the failure stage, the movement was classified as multiple rotational landslide. At the reactivation stage, the displacement occurs in blocks.