Study on the Influence of Slope Geometry on Slope Stability under the Impact of Climate Change

Abstract

In the Central and Central Highlands regions of Vietnam, characterized by predominant mountainous terrain and widespread distribution of weathered soils (clays and silty clays), prolonged intense rainfall events frequently induce severe slope failures, particularly along major transportation routes such as National Highways 1, 20, and 27C. This study assesses the influence of rainfall intensity and slope geometry on slope stability under rainfall infiltration. The analysis methodology is grounded in the theory of transient seepage, incorporating the soil-water characteristic curve (SWCC) equation proposed by Leong and Rahardjo [7], combined with the unsaturated soil shear strength model by Fredlund and Rahardjo. Numerical models were developed for slopes with heights Hs = 6–18 m, inclination angles β = 30°–45°, three representative soil types (saturated permeability ks = 10⁻⁴ to 10⁻⁶ m/s, effective cohesion c' = 10 kPa, effective friction angle φ' = 26°), and rainfall intensities Ir = 3–360 mm/h over a 24-hour duration. Results indicate that rainfall intensity (Ir) is the dominant factor affecting slope stability: when Ir ≥ ks, rapid saturation occurs, leading to instability (factor of safety FoS < 1) and FoS reductions ranging from 5.63% to 61.2%. In contrast, geometric factors exert a secondary influence: a 300% increase in slope height results in a 40.7% reduction in FoS; a 50% increase in inclination angle leads to FoS reductions of 11.4% to 26.2%