Saturated hydraulic conductivity of soils in a shallow landslide area in the Serra do Mar, Sao Paulo, Brazil

摘要

The Serra do Mar escarpment, which is located on the southern and southeastern coast of Brazil, is regularly hit by heavy rainfall that triggers numerous mass movements, particularly shallow landslides. Although several studies have investigated the relationship between these processes and the topographic, structural, lithological, and climatic constraints, there are few tests on the hydrological properties that directly influence the stability of slopes. Thus, the main objective of this study is to characterize the spatial distribution of saturated hydraulic conductivity (K-sat) and evaluate its influence on the initiation of shallow landslides in the Serra do Mar in Sao Paulo State (SP). Tests for K-sat were performed using the Guelph Permeameter in three scars in an experimental basin in the city of Caraguatatuba-SP, which was strongly affected by landslides in 1967. In each scar, two profiles were excavated (top and center) with tests at six depths up to 2.50 m. To better evaluate the variation in K-sat, the particle size and porosity values were used at the same depths. Forty-one K-sat values were obtained, and the values varied between three orders of magnitude (10(-6) to 10(-4) m s(-1)), with 80% concentrated between 10(-6) and 10(-5) m s(-1). In general, the profiles had lower K-sat values near the surface with a tendency to increase up to 5 m and significant hydraulic discontinuities between 1 and 2.5 m. It is believed, therefore, that a study of K-sat variation can provide important information on the rupture mechanisms within the Serra do Mar and define areas for real-time hydrological monitoring.