## 4 Results and Discussion
### Mechanical Properties of the Soil
#### 4.3.2. Aiterberg's Limits  
Aiterberg's limits are a set of index tests performed on finely grained soils to determine their relative activity to moisture. In this section, liquid limits, plastic limits, and plastic index are presented. It is important to state that soil samples collected across the study area were found to have similar Aiterbeg's limits. Indeed, the soil collected along the R523 roads were generally found to have 70% of the liquid limit on average (see Table 2). This result confirms that the soil is a very fine and clayey material with the ability to absorb large amounts of water within its pore spaces. Consequently, the accumulated water takes time to pass through or evaporate for this type of soil. Such soil also displays slipping and swelling characteristics especially in the presence of water. Conversely, this type of soil easily cracks when it dries up. Note that, although the fourth sample appears to present a less liquid limit, in reality, it falls under the same category. The causative factor for this is the slightly higher amount of silt particles present in the sample.  
Liquid limit alone cannot be used to draw a solid conclusion on the mechanical behavior of soil. It should be complemented with the analysis of the plastic limit and plastic index.  
The plastic limit can be regarded as an indicator of the water content at which the soil begins to crumble. Based on the results in Table 2, it can be seen that all samples have a plastic limit ranging between 26% and 37%. The soil material of the entire study area can therefore be categorized as of high plasticity in accordance with Table 2. Indeed, the thread could be rolled out down to 3.2 mm at any moisture possible during the experiment. The soil has the ability to contain water at a very low percolation rate; it becomes plastic even after a short rainfall and does not hold well at a high slope angle. Plastic limit results also correlate well with liquid limit ones.  
Talking about the plastic index, it can be said that it indicates the range of moisture content over which the soil is in a plastic state. Based on the work of [PERSON] [28], the plastic index is calculated as the numerical difference between the liquid limit and the plastic limit of the soil. Liquid and plastic limits are both dependent on the amount and type of clay in the soil, but the plasticity index is generally only dependent on the amount of clay present.  
The results in Table 1 show that the plasticity index of the material is at an average of 32% which is a classified as high plasticity index. This was confirmed by plotting the results in Table 1 on the plasticity index chart, as shown in Figure 7.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Samples** & **Liquid Limit (\%)** & **Plastic Limit (\%)** & **Plasticity Index (\%)** & **Description** \\ \hline Sample 01 & 71 & 37 & 34 & High plasticity \\ Sample 02 & 66 & 34 & 32 & High plasticity \\ Sample 03 & 70 & 37 & 34 & High plasticity \\ Sample 04 & 56 & 26 & 30 & High plasticity \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of [PERSON]’s limits of soil samples.  
It is important to note that the Atterberg's limits presented in this section mostly give a qualitative behavior of the soil subjected to different conditions.