# Parametric Analysis for 3D Modeling of Consolidation-Induced Solute Transport Using OpenFOAM
## 4 Results and Discussion
### Effects of the Degree of Saturation on Solute Transport  
Figure 22 shows that the pattern of solute concentration variation along the horizontal direction changes with different saturation levels (\(S_{t}\)). At the top (Figure 22a,b), concentrations differ more noticeably under varying saturation levels in the short term (1, 2, 3 years). At the 2-year mark, the concentration under low saturation conditions (square markers) is approximately 4% higher than that under high saturation conditions (triangle markers). In contrast, higher saturation (triangle markers) results in lower concentrations due to restricted drainage and slower solute migration. In the long term (5, 10, 20 years), concentrations stabilize, but lower saturation continues to show higher concentrations. In the concentration distribution at the middle and bottom positions (Figure 22c-f), solute migration is faster under high saturation conditions, particularly in the short term. To illustrate, at the 3-year mark, the concentration at the bottom position under high saturation conditions is approximately 30% higher than that under low saturation. This is because a higher saturation leads to larger changes in pore pressure, creating a stronger driving force that facilitates the migration of the downward solute. By the 10-year mark, the concentration difference between the two saturation conditions narrows to within 3%, indicating that the system is gradually approaching equilibrium. This behavior can be attributed to the influence of soil deformation during the consolidation process on solute migration paths and velocities. Under low saturation conditions,  
Figure 21: Horizontal displacement along horizontal cut line at \(z=1.5\) m over time for varying degree of saturation. Blue lines represent **Case 1**; black lines represent **Case 6**; red lines represent **Case 7**. faster drainage of water causes solutes to accumulate more easily in shallow layers, whereas, under high saturation conditions, the significant changes in the pore water pressure increase the driving force for solute migration. Although saturation affects the pore water pressure, if these changes are minor, the driving force for solute migration (e.g., hydraulic gradient) remains largely unchanged, resulting in similar solute concentration distributions. The faster downward migration of the solute under high saturation can be attributed to the greater variation in pressure, as the increase in water content amplifies the pressure changes, facilitating the movement of the solute to deeper layers. Figure 23 indicates that under different saturation conditions, the horizontal concentration distribution shows minimal variation and changes in saturation have not significantly influenced the overall solute migration pattern. This is likely because, under the study conditions, the horizontal diffusion process is primarily governed by the pore water pressure gradient, and the changes in saturation are not sufficient enough to cause notable alterations in the seepage field. In conclusion, the effect of saturation levels (\(S_{r}\)) on changes in solute concentration over time and depth is minimal. Although lower saturation shows slightly higher concentrations, particularly in the short term and at the top, the overall distribution trend is similar across different saturation levels, with negligible differences. Although saturation influences the water drainage and solute migration paths, it does not significantly alter the final solute distribution. The faster downward migration under high saturation may be driven by greater pressure variations, but in general, the impact of saturation on the solute distribution is limited. Figure 22: Distributions of concentration along (**a**,**b**) the top horizontal cut line at \(z=3\) m; (**c**,**d**) the middle horizontal cut line at \(z=1.5\) m; (**e**,**f**) the bottom horizontal cut line at \(z=0\) m for varying degree of saturation. Solid lines represent **Case 1**; squares represent **Case 6**; triangles represent **Case 7**.