## 3 Results
### Slope Instability Analysis Using FLACSlope
However, it has been shown that the slope does not collapse instantly; rather, it appears to fail gradually as the material undergoes phase changes, transitioning from solid to liquid to solid again, either because of water accumulation or a rise in the water table, either of which influence the resistance of the shear forces. However, water impact on stratified rock is not the only factor; there are other factors that the scope of the study is currently not intending to investigate. However, in some places, the increase in water presence may not necessarily mean that a landslide will occur. The understanding is that the top layers of the slope undergo phase changes with time but depend on the amount of rainfall filling the pore spaces; meanwhile, the separation becomes less resistant and failure can be initiated. The latter is also controlled by the existence of water streams cutting across certain lithologies in the area. The FLACSlope results are further represented graphically to assess the relationship between FoS and water presence (see Figure 17). Indeed, the relationship is observed to be proportional, implying that an increase in water volume on the slope results in saturation and phase transition, especially on the unconsolidated top layers of the slope, drastically reducing the Factor of Safety. A water volume increment increased the failure susceptibility by promoting the magnitude of shear stress over shear strength, as it is noted that the highest FoS obtained was for dry slope conditions, and the lowest FoS of 0.79 represents 2500 m\({}^{3}\) of water (wet conditions). The predicted results show how the presence of water and geological structures contributes to the decline in FoS and causes the slope to become less stable. Stated differently, landslides have a higher probability of happening in unconsolidated or highly fragmented material that is exceptionally damp. To sum up, the results of the simulations are supported by kinematic simulations, numerical simulations, and visual observations. The results also proposed that after significant rainfall, the top layer of the slope changes its phase  
Figure 16: Simulated FoS of the slope using FLACSlope in rainy conditions with the water table with 2500 m\({}^{3}\) of water. Note that the maximum shear strain simulated ranges between \(1.0\times 10^{-7}\) and \(2.329\times 10^{-6}\). \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
2.10 & 0 & \(1.0\times 10^{-6}\) & \(1.0\times 10^{-5}\) \\
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 a stratified slope with discontinuities. rapidly. As a result, the soil takes on the consistency of liquid. At this point, the connection between the particles weakens and the shear strength rapidly decreases. Eventually, there will be a distortion that manifests as a landslide. Based on observations, it was noted that post-landslides create land fractures 10 m long. The uncontrolled surface drainage water is channelled toward these fractures, resulting in more unstable slopes.