Geological-structural mapping of rock slopes applied to stabilization projects: case study of Serra das Antas, BR-470, Rio Grande do Sul

Landslides constitute a recurrent natural hazard globally, severely impacting socio-economic and environmental systems. In Brazil, and particularly in the road infrastructure of Rio Grande do Sul, this vulnerability was dramatically evidenced by the extreme events of 2024. This study addresses the instability of 43 rock slopes along the BR-470 highway in the Serra das Antas region (between Bento Gonçalves and Veranópolis), a critical area with a history of rainfall-induced landslides structurally controlled by brittle discontinuities (columnar and sub-horizontal joints). The core objective was to perform a detailed geological-structural mapping of the Serra Geral Formation basaltic rock masses to diagnose instability patterns and define optimized intervention protocols. The methodology employed an integrated approach, combining detailed field geological-geotechnical mapping with kinematic and geomechanical analyses (limit equilibrium via Mohr-Coulomb and Hoek-Brown criteria). A geological-geotechnical compartmentalization of the rock masses was developed to reflect the complex structural heterogeneity, and the rock mass quality was assessed and classified using the GSI and RMR indices. Structural and kinematic analysis confirmed the prevalence of instabilities conditioned by these discontinuities, resulting in rockfall as the dominant failure mechanism (93% of cases), frequently associated with wedge failure (61%). The proposed stabilization solutions — including high-tensile steel mesh with anchored bolts and dynamic barriers — replace the traditional homogeneous treatment with a compartmentalized approach. It is concluded that compartmentalization constitutes an effective model, allowing technical and economic adjustments of the interventions to the specific geomechanical conditions of each segment, thereby increasing the reliability of the results and enhancing road safety.