Evaluation of Geotechnical Parameters of Slopes at Blumenau, Santa Catarina, Brazil

The state of Santa Catarina, Brazil, has climatic, biological, geomorphological and geological characteristics that contribute directly to the occurrence of landslides. From the geological point of view, colluvial materials resulting from landsliding deposited in the lower parts of the slopes are denominated as hillslope deposits although they do not necessarily originate from the same rock. This study evaluated the geotechnical parameters of the slopes at Blumenau, where intense rainfalls and potentially unstable soils are present on steep hillsides and give rise to unstable colluvial slopes below. These factors resulted in a large number of slopes covered by colluvial deposits. However, in geotechnical mapping these kinds of materials are treated as “hillslope deposits” units with similar behaviors even though they have different geological-geotechnical evolutions and have experienced distinct processes of pedogenesis. The paper covers the classification as colluvial soils and landslides, as well as the use of geotechnical laboratoratory tests and geotechnical mapping. Evaluation of the geotechnical behavior of the soils was based on geotechnical characterization tests and drained direct shear tests in which parameters of cohesion and internal friction angle were obtained. Thus, the goal of this study was to understand the variability of the geotechnical parameters of these colluvial soils that formed as “hillslope deposits” units according to Davison Dias (1995) methodology, so that they could be classified based on their lithotypes. The study results will help in urban planning in Blumenau and contribute to safety and predictability of areas subject to possible landslides.