Análise numérica da estabilidade de talude natural sob diferentes condições pluviométricas e de fraturamento do maciço rochoso subjacente

Abstract

The city of Petrópolis, located in the mountainous region of the state of Rio de Janeiro, is highly susceptible to landslides triggered by intense rainfall, due to its steep relief, geological–geotechnical characteristics, and unplanned urban occupation. In this context, the present study aims to assess, by means of transient numerical flow modelling, the influence of rainfall conditions and rock mass properties on the stability of a slope representative of Monte Florido, in Petrópolis/RJ, composed of residual soil over fractured rock. The simulations were performed with the RS2 finite element software, considering the unsaturated behaviour of the soil and the Shear Strength Reduction (SSR) method to determine the factor of safety, expressed by the Strength Reduction Factor (SRF). Seven rainfall scenarios were analysed, defined from different temporal distributions and probabilities of occurrence of landslides representative of the municipality, as well as three rock mass permeability conditions (k = 1×10⁻³, 1×10⁻² and 1×10⁻¹ m/s), representing different degrees of fracturing. The results indicated a progressive reduction in the factor of safety over time, with greater loss of stability in scenarios of intense rainfall and in rock masses with higher hydraulic conductivity. The increase in pore pressure at the soil–rock interface was decisive for instability, concentrating shear deformations in this region. In more permeable rock masses, possible numerical inconsistencies were observed, whereas for lower permeabilities the model showed a coherent and gradual response, with an orderly reduction in the factor of safety and physically consistent behaviour. Despite the numerical limitations observed, the study has the potential to improve the identification of critical conditions and timing of instability and to support more robust analyses for landslide prediction.