## 3 Results and Discussion
### Effect of Antecedent Saturation  
The analysis of the rainfalls of 2.5 mm/h, 5 mm/h, and 10 mm/h for varying initial saturation degrees were evaluated. The resulting FoS values with respect to the time for the FLAC sample are presented in Figure 5. Since the FoS values for the soil given in this study were found to be higher, the detailed evaluation on the effect of the antecedent saturation degree was only made for the results of the FLAC sample for practical purposes. It is also a reminder that the main purpose of this study is not the soil properties or the comparison of them, but how to use them when evaluating the natural unsaturated slopes and how to follow the procedure given in this study regardless of the soil type. This is because there can be huge variations in the soil properties of slopes and each condition should be evaluated eventually. To achieve a realistic evaluation depending on the anticipated critical rainfall times, the calculated threshold amounts of times were also evaluated. Thus, the calculated threshold amounts of heavy rainfall at standard times given on the TSMS web site ([PERSON] et al., 2018) are utilized. These durations are indicative of the typical length of precipitation under standard conditions. According to the given thresholds of TSMS, the expected time for rainfalls of 2.5 mm/h, 5 mm/h, and 10 mm/h are found to be 24 h, 9.1 h, and 2.5 h, respectively. And the critical times given for each instance of rainfall are marked with a vertical dashed line in Figure 5a-c. It can be clearly seen that no failure was expected within the critical time durations even when the thresholds would be doubled. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Initial FoS for**} & \multicolumn{5}{c}{**Initial Saturation Degrees**} \\ \cline{2-6}  & **S = 40\%** & **S = 45\%** & **S = 50\%** & **S = 55\%** & **S = 60\%** \\ \hline FLAC sample & 1.428 & 1.345 & 1.291 & 1.236 & 1.182 \\ This study & 1.502 & 1.420 & 1.338 & 1.283 & 1.228 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Factor of safety values of the soils for each initial saturation degree. Figure 5: The slope stability analysis when subjected to rainfalls of (**a**) 2.5 mm/h, (**b**) 5 mm/h, and (**c**) 10 mm/h. A decrease in FoS was determined when the initial saturation degree increased due to the decrease in matric suction and its positive effect on the soil strength. Moreover, a similar decrease in FoS with increasing durations was determined as well. When the rainfall of 2.5 mm/h was applied to each model with varying initial saturation degrees, the time for failure was dramatically changed (Figure 5a). The time for failure in rainfall conditions was found to be approximately twice as long for samples with an initial saturation degree of 40% as for those with a saturation degree of 60%. If the initial saturation degree was held constant, in the 60% instance, the time for failure against 2.5 mm/h, 5 mm/h, and 10 mm/h are found to be 50, 24, and 10 h, respectively. The possibility of a 2.5 mm/h rainfall for 50 h is higher than 5 mm/h for 24 h and 10 mm/h for 10 h in real conditions. The data indicate that slope failure due to rainfall is more likely to occur when there is a constant light rainfall and a long duration of rainfall in this condition. Similar results were given in the study of [PERSON] and [PERSON] [PERSON] and [PERSON] (2013). The graphics in Figure 5 demonstrate that the rainfall intensity and duration are not independent variables. Furthermore, when the slope stability was considered, the initial saturation degrees are essential to begin with, which are likely to change significantly according to weather conditions. Furthermore, when examining a slope stability issue, it becomes evident that evaluating the stability based on a single saturation condition is not a sufficient approach. The impact of saturation levels on the failure mechanism demonstrates the crucial importance of in situ volumetric water content measurements for slope stability assessments.