Annually, several billion dollars are spent to mitigate landslides and rehabilitate structures affected by slope failures. Such instabilities may arise from several factors, including complex slope terrain geometry, varying geomorphology, seasonal groundwater fluctuations, changes inriver water levels, prolonged waterlogging, and development of intermittent slickensides.Incorporating these effects into slope stability analysis can be challenging, requiring thoroughfield investigations and geotechnical assessments, as well as performing 2D and 3D slope stability analysis to accurately estimate reliable factors of safety. This paper presents a case study on stability analysis for a slope adjacent to US Highway 75 in Minnesota. This site is characterized by the interactions between transportation infrastructure and the Sandhill River passing through the region to join the Red River of the North. To analyze the impact of complex slope geometry and its interactions with infrastructure, aerial remote sensing data was obtained to generate a detailed 3D slope geometry, which was further processed to conduct 2D and 3D slope stability analyses using Spencer’s method and probabilistic methods using Monte Carlo Simulations, Latin Hypercube Sampling, and Response Surface Method. The results from deterministic slope stability analysis show that the slope factor of safety was higher when using peak undrained shear strength. In addition, the probability of failure of the slope using 3D and2D analyses at peak undrained shear strength case was observed to be negligible compared to the case with residual undrained shear parameters. The critical factor of safety values of two hypothetical extreme scenarios for the area were considered to gain an in-depth understanding of the risk posed to the transportation infrastructure. The present paper summarizes the critical role of incorporating 3D slope stability analysis and pore-water pressure conditions to account for boundary effects and complex failure mechanisms.
