Numerical Modeling of Residual Soil Slope Stability Under Prolonged Extreme Rainfall in Mountainous Terrain Using Three-Dimensional Finite Element Method
DOI:
https://doi.org/10.69855/sipil.v2i2.702Keywords:
Residual Soil, Slope Stability, Rainfall Infiltration, 3D Finite Element Method, Factor of Safety, Unsaturated SoilAbstract
Rainfall-induced landslides in residual soil slopes are major geotechnical hazards in tropical mountainous regions, where prolonged rainfall reduces matric suction and soil shear strength. This study investigated the hydro-mechanical response and stability of a representative residual soil slope under prolonged extreme rainfall using a three-dimensional finite element method (3D FEM). Coupled transient seepage–deformation analysis was conducted using the van Genuchten soil–water characteristic curve (SWCC) and shear strength reduction method (SRM) to evaluate the time-dependent factor of safety (FS). Four rainfall scenarios involving 50-year and 100-year average recurrence interval (ARI) events with durations of three, five, and seven days were simulated, including antecedent rainfall conditions. The results showed that the wetting front advanced non-linearly, while pore-water pressure increased from an initial suction of approximately −45 kPa to near-positive values within 120–150 hours. The FS decreased from 1.62 under dry conditions to 0.79 under the most critical scenario, indicating slope failure. The critical slip surface developed at a depth of 8–10 m, corresponding to the residual soil–weathered rock interface. These findings demonstrate that rainfall duration and antecedent moisture conditions significantly influence slope stability. The proposed 3D FEM framework provides a useful basis for rainfall-based early-warning systems and slope reinforcement planning.
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