## 3 Results and Discussion
### Effect of Initial Degree of Saturation  
The impact of the initial degree of saturation on the mechanical properties of sand-clay mixtures with varying sand content was investigated. The maximum dry density was calculated for each percentage of sand using the standard Proctor test, and it was found that the maximum dry density increased with an increasing percentage of sand, as depicted in Figure 5. The relationship between \(q_{u}\) and \(E_{t}\) with the degree of saturation (_SR_) was studied separately for each sand percentage, and the results are presented in Figure 13. A sharp decrease in both the unconfined compressive strength and elasticity modulus was observed as _SR_ increased, and the decrease became less severe as _SR_ increased due to the filling of soil pores with water and the corresponding decrease in suction forces.  
Figure 13A: This graph is a scatter plot with a series of descending lines, each line representing the trend for a specific percentage of sand (_Fs_) within the soil mixture. The x-axis represents _SR_% ranging from about 30% to 100%, and the y-axis represents \(q_{u}\) measured in kilopascals (kPa), which ranges from approximately 0 to 1800 kPa. The general trend shows that as saturation increases, the unconfined compressive strength decreases sharply initially and then levels off, indicating a reduction in strength gain as saturation approaches 100%.  
Figure 13B: This graph is also a scatter plot with descending lines, similar to Figure 13A, but it depicts the change in elasticity modulus (\(E_{t}\)). The y-axis has a much larger scale, ranging from 0 to 160,000 kPa, reflecting the higher values typical of elasticity modulus measurements. The lines follow the same color and style codes as Figure 13A and show the same trend of reduction in the elasticity modulus with an increase in soil saturation. The sharp decline in modulus suggests that the material becomes significantly less stiff and more deformable as it becomes wetter, which is a critical consideration for soil mechanics and engineering.  
The trend in Figure 13A demonstrates a clear inverse relationship between _SR_ and \(q_{u}\) of the soil. As the saturation increases, \(q_{u}\) decreases across all sand content percentages (_Fs_), indicating that soil strength is compromised by the presence of water. The results show a steep decline in strength at lower saturation levels, which then tapers as saturation approaches full capacity. The various lines for different _Fs_ percentages suggest that the mixtures with more added sand tend to retain higher strength at the same saturation level compared to those with less sand. This behavior implies that soils with lower sand content are more susceptible to strength loss with increased water content.  
In Figure 13B, the elasticity modulus (\(E_{t}\)) exhibits a similar downward trend with increasing soil saturation, highlighting a decrease in soil stiffness. The lines plotted for different \(F\)s percentages all slope downward, indicating that as the soil becomes more saturated, its ability to elastically deform and return to its original shape is diminished. The sharpness of the slope varies with the percentage of added sand, with higher sand content mixtures showing a slightly less severe reduction in \(E_{t}\). This reduction in elasticity with increased saturation is crucial for civil engineering applications, as it affects how soil will behave under structural loads, with potential implications for the design and stability of foundations and other soil-structure interactions.