Influence of Rainfall Temporal Patterns on Seepage Response and Stability of Unsaturated Slopes

Abstract

Rainfall-induced seepage variation strongly affects the internal mechanical condition of unsaturated slopes. However, the influence of temporal precipitation patterns on seepage control dynamics and the evolution of slope stability remains insufficiently understood. This study investigates the effects of rainfall temporal distribution on pore water pressure accumulation and unsaturated slope stability. Four distinct rainfall patterns (uniform (JY-2), normal (JY-1), exponential (JY-3), and compound (JY-4)), each with identical total rainfall, were used to develop a numerical seepage model for calculating seepage flow. Pore water pressure was monitored at the slope crest, mid-slope, and toe, and together with the factor of safety (FOS), was used to assess overall slope stability. Simulation results reveal that different rainfall timing conditions noticeably influence internal seepage migration and the associated stability response of the slope. Pore water pressure propagates from the slope toe toward the crest, exhibiting a distinct time lag. Within the first 48 h, pore pressure at the toe increases rapidly from approximately −70 kPa to near-saturated conditions, whereas the FOS changes only slightly. Among the scenarios, the exponential rainfall pattern produces the fastest hydraulic response near the slope toe, whereas the factor of safety shows only minor variation within the 48-hour simulation period. These findings highlight the importance of considering rainfall temporal distribution in slope stability assessment and landslide hazard evaluation.