## 3 Results and Discussion  
### Soil-Water Characteristic Curve (SWCC)  
The partially saturated condition is represented based on the SWCC. This curve describes the relationship between the soil's water content and matric suction, which is the energy required to extract water from the soil [25; 26]. Figure 6 shows the experimental curve used in this research, which enabled the analysis of unsaturated soils. This curve was taken from the work of [PERSON] et al. [13; 27] (blue squares) and the [PERSON] model [28], used by Plaxis2D(r), and it was fitted according to the following equation:  
\[Sr(\psi)=S_{\text{res}}+(S_{sat}-S_{\text{res}})\big{[}1+(g_{a}|\psi|)^{g_{a}} \big{]}^{g_{c}} \tag{12}\]  
\[g_{c}=\frac{1-g_{n}}{g_{n}} \tag{13}\]  
where Sr is the degree of saturation, Sres is the residual saturation, Ssat represents the degree of saturation at which the pores remain filled with water, and g\({}_{a}\) and g\({}_{n}\) are fitting parameters that relate to the air entry value and the rate at which water is being extracted from the soil [29; 30].  
This equation describes the variation in the degree of saturation as a function of suction, modeling the soil's behavior in terms of water retention under different moisture levels. However, in partially saturated soils, not all suction directly impacts effective stress [21]. To address this difference, the concept of effective saturation is incorporated, representing the portion of water retained in the soil that affects effective stress [22].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Saturated** & & **Unsaturated Sr = 60\%** & **Unsaturated Sr = 99\%** & **Unsaturated Sr = 80\%** \\ \hline
**Load [LPa]** & **Soft Soil** & **Hardening Soil** & **Soft Soil** & **Hardening Soil** & **Hardening Soil** & **Hardening Soil** \\ \hline
10 & SS.Sat\_10 & HS.Sat\_10 & SS.60\%\_10 & HS.60\%\_10 & HS.99\%\_10 & HS.80\%\_10 \\
25 & SS.Sat\_25 & HS.Sat\_25 & SS.60\%\_25 & HS.60\%\_25 & HS.99\%\_25 & HS.80\%\_25 \\
50 & SS.Sat\_50 & HS.Sat\_50 & SS.60\%\_50 & HS.60\%\_50 & HS.99\%\_50 & HS.80\%\_50 \\
100 & SS.Sat\_100 & HS.Sat\_100 & SS.60\%\_100 & HS.60\%\_100 & HS.99\%\_100 & HS.80\%\_100 \\
200 & SS.Sat\_200 & HS.Sat\_200 & SS.60\%\_200 & HS.60\%\_200 & HS.99\%\_200 & HS.80\%\_200 \\
400 & SS.Sat\_400 & HS.Sat\_400 & SS.60\%\_400 & HS.60\%\_400 & HS.99\%\_400 & HS.80\%\_400 \\
800 & SS.Sat\_800 & HS.Sat\_800 & SS.60\%\_800 & HS.60\%\_800 & HS.99\%\_800 & HS.80\%\_800 \\
1600 & SS.Sat\_1600 & HS.Sat\_1600 & SS.60\%\_1600 & HS.60\%\_1600 & HS.99\%\_1600 & HS.80\%\_1600 \\
3200 & SS.Sat\_3200 & HS.Sat\_3200 & SS.60\%\_3200 & HS.60\%\_3200 & HS.99\%\_3200 & HS.80\%\_3200 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Model matrix.  
The calibration process of the SWCC for its use in the numerical model was as follows:  
1. The Van Genuchten Equation (9) was plotted by varying the fitting parameters (ga, gn, and gc) until achieving the best possible match with the experimental curve.
2. Using the initial degrees of saturation for each unsaturated model, the corresponding matric suction was extracted based on the experimental curve and Plaxis(r).
3. Matric suction values from the experimental model and the program were compared to achieve the smallest possible variation.
4. The fitting parameters were input into each numerical model before execution.
5. The modeling results in terms of initial saturation and matric suction were consistent and within the ranges of the experimental method.  
Table 5 shows how the degree of saturation increases due to volumetric deformations as the applied stress varies.