## 3 Results and Discussion  
### Effect of Rainfall Duration on the Degree of Saturation  
In Figures 5 and 6, due to rainfall infiltration into the slope, a significant increase in the degree of saturation was observed in both soils. Initially, the slope's degree of saturation was 70%. However, as rainfall infiltrates, this saturation progressively increases, reaching values close to 100% at the upper part of the slope. This increase in saturation is not limited to the surface layers; in cases of longer-duration rainfall, the increase in saturation propagates deeper into the slope. As shown in Figure 6 (see red arrow), an overload is observed on the slope face for the same rainfall durations of 18 and 24 h in SW-SM soil. This overload represents the accumulation of rainwater that could not infiltrate and instead flows over the slope surface [11; 12; 20]. Figures 7 and 8 present the graphs of effective saturation versus time at the control points of the model (see Figure 4). These graphs provide insight into how saturation varies over time at each specific slope height. This analysis was crucial for observing the increase  
Figure 4: Positioning of nodes in Plaxis and boundary and flow conditions. in saturation as time progressed, offering a detailed understanding of the slope's behavior under different levels of water infiltration. This graph shows how the effective saturation of the SP-SM soil varies at different depths of the slope (12 m, 9 m, 6 m, 3 m, and 0 m) as a function of rainfall duration. Each curve represents a specific elevation within the soil profile, where the progressive advancement of infiltration from the top of the slope toward the base can be observed. The data should be interpreted from the top to the bottom of the slope: the higher the elevation, the earlier saturation occurs; the lower the elevation, the more the effect is delayed or almost negligible, highlighting how water progressively moves through the soil profile. This graph, like the previous one, shows how the effective saturation varies--this time for the SW-SM soil--at different depths of the slope (12 m, 9 m, 6 m, 3 m, and 0 m) throughout rainfall. Each curve represents a specific elevation within the soil profile, where the progressive advancement of infiltration can be observed, although this occurs more slowly and gradually compared to the SP-SM soil. The data should be interpreted from  
Figure 5: Increase in saturation of SP-SM soil for rainfall durations of 8, 12, 18, and 24 h.  
Figure 6: Increase in saturation of SP-SM soil for rainfall durations of 8, 12, 18, and 24 h. Grid lines represent the finite element mesh used for numerical simulation. Red arrows indicate the direction of water infiltration. The blue areas correspond to fully saturated soil. the top to the bottom of the slope: the upper zones become saturated first; meanwhile, at deeper levels, the increase occurs later and more gradually, highlighting the greater water retention capacity of the SW-SM soil. The slope analyzed with SP-SM soil (see Figure 7) shows that water infiltration initially occurs at the upper levels. At a height of 12 m, saturation increases rapidly, stabilizing at 93.5% in 1.2 h. At 9 m, the process is delayed, beginning to saturate at 6 h and reaching 94% at 9.6 h. At 6 m, saturation starts later, at 14.4 h, stabilizing between 93-94% at 18.6 h. At lower levels, such as 3 m, saturation progresses more slowly, significantly increasing only at 21.6 h, with a maximum of slightly above 80%. Finally, at the base of the slope  
Figure 8: Effective saturation vs. time for SW-SM soil at heights H = 12 [m], H = 9 [m], H = 6 [m], H = 3 [m], and H = 0 [m]. Figure 7: Effective saturation vs. time for SP-SM soil at heights H = 12 [m], H = 9 [m], H = 6 [m], H = 3 [m], and H = 0 [m]. (0 m), saturation remains at the initial condition consistently throughout the analysis period, indicating that infiltration does not significantly reach this level.