## 4 Results and Discussion
### Initial Results of the Field Observations  
The initial walkabout showed that all discovered landslides were located along with the road benches or sidewalls. The ongoing road construction along this mountainous area also appeared to alter the surface drainage patterns, create unstable slopes, and increase runoff (see Figure 3).  
In simple terms, the first empirical observation suggested that improper road construction could be the reason for the formation of water pools at the foot of the cut-slope. This became a non-negligible driving force for accelerated slope failures. Second, altered drainage patterns led to an increased rate of surface runoff and increased probability of water washing soil down to the road. As a result of this, the surface drainage ditch was blocked while the foot of the slope became waterlogged. The rapid saturation of soil ensued also contributing to the frequent occurrence of landslides. This destabilized the R523 road and the side-cast material downslope; this also made the slope steeper than before. Consequently, undercut natural slopes become unstable. Shear stresses in the soil within the slope increase with increased probability for failure [36].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multicolumn{4}{c}{**Layers of the Soil Slope**} \\ \cline{2-5}  & **Lower Layer** & **Upper Soil (Area A)** & **Upper Soil (Area B)** & **Upper Soil (Area C)** \\ \hline
**Unsaturated Density (kg/m3)** & 1900 & 1600 & 1400 & 1300 \\
**Saturated Density (kg/m3)** & 2200 & 1900 & 1700 & 1600 \\
**Porosity** & 0.2 & 0.3 & 0.5 & 0.4 \\
**Cohesion (Pa)** & 10,000 & 5000 & 8000 & 6000 \\
**Friction angle (°)** & 30 & 20 & 25 & 27 \\
**Soil Particle Density (g/cm3)** & 2.8 & 2.65 & 2.63 & 2.66 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Material properties of the layers used in the model.  
Figure 3: Downward movement of material (soil or rocks) along R523 road, (**a**) occurrences of post landslides along the R523 road; (**b**) Tension cracks observed during the reconnaissance survey; (**c**) evidence of an undercut natural slopes become unstable; (**d**) Block of the slope material sliding toward the road.  
Third, contrary to local accounts, evidence of previous landslides was noticed also where certain slopes were deemed inactive. This prompted the implementation of mitigating measures to limit further slope failure (landslides). A gabion wall was erected to prevent future landslides. The gabion walls were noted to be effective where two-tiered steps were employed and to fail otherwise. The ineffectiveness of the gabion translated into the collapse of the walls or the wash-away of soil material. In other instances, the failure of the gabion was created to the interruption of traffic due to soil slides blocking the road.  
Another factor believed to contribute significantly to slope failure along the study areas is water pressure. Indeed, [PERSON] and [PERSON] [36] have shown that water naturally fills the cracks developed on the surface of the slope. The water then greatly decreases the shear strength of the soil as pore pressure within the slope increases. Supporting observations also showed that several cracks and a number of short streams were present in most areas with pronounced slope failure.  
In summary, the initial field observations enabled us to build an empirical picture of the occurrence of landslides along the R523 road. There is strong evidence that the cross-section profile of the constructed road encourages retention, instead of the flow, of water around the area. And because the majority of landslides occur during the rainy season (i.e., in December and January), the weathering profile of the region is to be further explored. Once this is done in subsequent sections, a correlation between landslide occurrences and rainfall statistics may be established. The benefit of the analysis would be a more realistic simulation of the soil and rock mass.