Abstract: The examination of slope stability is a crucial facet in the field of slope engineering, with rainfall identified as a primary hazard for inducing instability. The investigation into how rainfall infiltration impacts slope stability is of utmost importance for devising effective strategies to prevent and mitigate the risks associated with landslide phenomena. In this regard, the current study leverages the advanced capabilities of COMSOL Multiphysics software to develop a comprehensive model that intricately couples unsaturated seepage and stress mechanics within slopes. Through the application of the strength reduction method, this research delves into the complex interplay between rainfall and its effect on the stability of slopes. The findings from this study shed light on the fact that rainfall triggers a noticeable shift in the slopes downwards, which, intriguingly, do not revert to their original state even after the rainfall has ceased, thereby elevating the risk of slope failure. When it comes to determining the stability coefficient utilizing the strength reduction method, it is observed that the choice of methodology for instability assessment can lead to varying outcomes in terms of stability coefficients, thus highlighting the importance of selecting a method that best fits the specific circumstances at hand. Additionally, the research points out that rainfall significantly lowers the stability coefficient of slopes, and although there is a slight improvement once the rainfall stops, the degree of recovery is limited. This underlines the inherent challenges in fully restoring slope stability to its pre-rainfall condition, emphasizing the persistent impact of rainfall on the structural integrity of slopes and the complex challenges involved in mitigating such effects.

Key words: Rainfall Infiltration, Unsaturated Seepage-Stress Coupling, Slope Stability Analysis