In situ undrained shear strength for cutting slopes erodibility estimation: case study in the Quadrilátero Ferrífero region, Brazil

Erosion is a natural relief modeling process that is influenced by several factors. Among these, we highlight the soil properties, designated by the specific concept of erodibility. Most of the existing methods for quantifying erodibility are based on field plots or indirect procedures developed from farmland approaches and methodologies limited to other study conditions such as slopes, where soil structure is different. Therefore, the objective of this study is to investigate the erodibility of cutting slopes in the Quadrilátero Ferrífero region, Brazil, and its relationship with soil properties, using the hand vane test to determine undrained shear strength (S_U) and associating its values with the erodibility factor K. The results show that S_U has significant correlation with the fine soil particles, especially clay and silt. In addition, properties responsible for the increase in S_U decrease erodibility factor K. The mean weight diameter, geometric mean diameter, and aggregate stability index parameters show that aggregate diameter and stability are associated with higher S_U and, conversely, lower K values. In addition, chemical properties, especially pH, also interfere in the results, however, in lower proportion when compared with the physical indexes. Finally, the undrained shear strength has a significant negative correlation with erodibility factor K, both in non-erodible (R² = 0.6770, p value < 0.01) and erodible (R² = 0.7885, p value < 0.01) soils, showing promising methods in the diagnosis of potentially erodible soils.