## 4 Results and Discussion
### Simulation of the Effects of Rainfall Intensity on Slope Stability
#### 4.5.2 Simulation Case of a Silt Clay Soil  
The second simulations were undertaken to verify the performance of the typical clay loam soil subjected to different conditions (sunny and rainy). Similarly, from the previous discussion when simulating using SLIEDEs, in the sunny conditions water table with a volume of 1000 m\({}^{3}\) was used followed by a rainy condition with a water table with a volume of 2500 m\({}^{3}\). On the other hand, the simulation using FLACSlope has considered the entire accumulated volume of the water table from 1000 to 2500 m\({}^{3}\). The results of the simulation are discussed in the subsections below. Simulations of the FoS Using SLIDE Model under Rainy Conditions in Silt Clay Soil Slope  
The results of the simulation (see Table 4) denoted the FoS values range from 1.424 to 1.717, the results indicate that the simulated slope is stable. Similarly, with the previous discussion on clay soil, a correlation between visual observation and the simulated results were performed, it noted that there is some correlation between the two, however it was also noted that although the model estimated stable slope, the stability of the slope is usually compromised when subjected to heavy rainfall which increases the volume of the water table. However, the extent of slope failure is moderate compared to pure clay soils. Detailed simulation of the slope when subjected to an increase in the water table of 2500 m\({}^{3}\) is documented below. Simulations of the FoS Using SLIDE Model under Rainy Conditions in Silt Clay Soil Slope  
Figures 19-22 give a summary of the simulated scenarios as well as the associated FoS for the silt clay soil. It can be seen that FoS values range from 0.264 to 0.350. So, regardless of the computational methods used, the slope in this silt clay soil is deemed unstable. This confirms that the selected type of slope is highly prone to landslides in the area. Furthermore, it was also noted that [PERSON]'s and Corp of Engineers' methods produced closely comparable FoS values. However, by and large, FoS estimates are similar to within \(\pm\)0.2 units (i.e., 0.264 \(<\) FoS \(<\) 0.350). Figure 19: Safety factor simulated for rainy conditions in silt clay soil slope using (**a**) [PERSON]’s simplified method and (**b**) [PERSON]’s simplified method. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Factor of Safety (FoS)**} & \multirow{2}{*}{**Volume of Rainfall (m\({}^{3}\))**} & \multicolumn{2}{c}{**Slope Max Shear Strain (Displacement in Shear)**} \\ \cline{3-4}  & & **Minimum Shear Strain** & **Maximum Shear Strain** \\ \hline
1.42 & 1000 & \(5.0\times 10^{-8}\) & \(8.30\times 10^{-7}\) \\
1.37 & 1500 & \(1.0\times 10^{-8}\) & \(4.007\times 10^{-5}\) \\
1.17 & 2000 & \(1.0\times 10^{-7}\) & \(2.166\times 10^{-6}\) \\
0.79 & 2500 & \(1.0\times 10^{-7}\) & \(2.329\times 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: General results of FLACSlope simulations in clay soil slope. Simulations of the FoS Using FLACSlope (FDM) Model under Sunny to Rainy Conditions in Salt Clay Soil Slope  
Figures 23-26 and Table 6 gives a summary of the simulated scenarios as well as the associated FoS for the silt clay soil from sunny to extreme rainy conditions. It can be seen that FoS values range from 1.94 to 1.26. The simulation has shown that the slope is stable in sunny conditions, however, the stability of the slope reduced gradually as the water table increases due to extreme rainfall. This result give the impression that, regardless of the computational methods used, the slope in this silt clay soil is deemed unstable when exposed to extreme rainfall. Further compromise with the FEM method has revealed that the slopes within the selected areas are prone to failure especially when the rainfall occurs continuously. Figure 21: Safety factor simulated for rainy conditions in silt clay soil slope using **(a)** Corp of Engineers’ Number Two method and **(b)** Lower Karafiath method.