Abstract
Heavy rainfall events can trigger failures in numerous soil slopes. During such periods, groundwater levels rise, increasing pore water pressure and reducing slope stability. This study aims to examine variations in pore water pressure and the factor of safety associated with slope stability. The subsurface water flow is numerically modeled as a two-dimensional, saturated–unsaturated, transient flow. Pore water pressure is calculated using the finite element method, while the factor of safety is evaluated through the limit equilibrium method. To simulate the unsteady flow, a time duration of 4 days is used with a time step of 0.1 days. The rainfall duration was assumed to be 24 h. The intensities of different rainfall events are used as input fluxes at the soil surface. The soil-water characteristic curve (SWCC) is used. The results indicate that varying rainfall intensities produce distinct effects on the soil moisture profile. As precipitation intensity increases, the factor of safety for slope stability decreases. This reduction is most pronounced during the first 24 h of rainfall within the three-day period, and after the rainfall ceases, the rate of decrease becomes more gradual. For example, for a rainfall intensity of 2.04 mm/hour and a duration of one day, the factor of safety for slope stability was 1.853, and at the end of the fourth day, it was 1.743. In other words, the factor of safety decreased by 5.9%.