Slope stability evaluation and quantitative landslide risk assessment of road cut-slopes on the D400 highway, southwestern Turkey.

Landslides are a common natural hazard in southwestern Turkey, threatening lives and damaging infrastructure, particularly highways in mountainous regions. This study evaluates landslide risks along the D400 Highway, which traverses complex geological terrain characterized by failure-prone cut slopes. Slope stability was analyzed using rock mass classification (SMR), combined with finite element analysis (FEM) and shear strength reduction (SSR), yielding consistent results. Factors of safety (FOS) were calculated using both the Generalized Hoek–Brown (GHB) and Mohr–Coulomb (MC) criteria for regional hazard assessment. The slope with the lowest stability exhibited FOS values decreasing from 1.32 under static-dry (low-risk) conditions to 0.91 under dynamic-saturated (high-risk) conditions when using the GHB criterion. In contrast, MC-based values were higher, ranging from 1.65 to 1.18. Overall, MC yielded FOS values approximately 1.4 to 1.7 times higher than those from GHB across all conditions. Slopes were then classified into hazard levels based on stability grades and safety factors to support risk management. Accordingly, 44.4% of the studied slopes were classified as having very high or high stability by the GHB criterion, compared to only 22.2% under the MC criterion. Finally, a quantitative landslide hazard assessment incorporating major regional causative factors demonstrated that the GHB criterion is the most suitable for slope stability analysis in jointed and heterogeneous rock masses. [ABSTRACT FROM AUTHOR]