# Parametric Analysis for 3D Modeling of Consolidation-Induced Solute Transport Using OpenFOAM
## 4 Results and Discussion
### Effects of the Poisson Ratio on Solute Transport  
As illustrated in Figure 28, Poisson's ratio affects changes in the concentration of the solute over time and depth; the overall magnitude of these changes is relatively small. Regardless of location, center or edge, the trends in concentration distribution remain similar. A lower Poisson ratio restricts the lateral expansion of the soil, leading to more pronounced vertical deformation and higher vertical stress. This increases pore water pressure, accelerating vertical solute migration and resulting in higher concentrations in the upper layers. In contrast, a larger Poisson ratio allows greater lateral expansion, dispersing vertical stress, reducing pore water pressure, and slowing the migration of the solute, leading to a lower accumulation of the solute. As shown in Figure 34, in the short term (1-3 years), a smaller Poisson ratio results in faster accumulation of solutes in the upper layers, leading to a rapid increase in concentration. At the 2-year mark, the upper-layer concentration under a smaller Poisson ratio is approximately 5% higher than that under a larger Poisson ratio. This is because a smaller Poisson ratio restricts lateral expansion, leading to vertical stress concentration and an increase in pore water pressure, which accelerates solute migration in the vertical direction. In the long term (5-20 years), while concentrations eventually stabilize, a smaller Poisson ratio continues to produce higher solute levels, especially in the lower layers. For example, at the 10-year mark, the lower layer concentration under a smaller Poisson ratio is approximately 50% higher than that under a larger Poisson ratio. This trend indicates that under a smaller Poisson ratio, the delayed effects of the consolidation process gradually drive solute migration deeper, resulting in solute accumulation in the lower layers. In contrast, a larger Poisson ratio disperses vertical stress, slowing down the consolidation process and inhibiting downward solute migration. At different depths, a smaller Poisson ratio leads to higher concentrations of solutes in the upper and middle layers as vertical stress continues to drive solute accumulation. This effect intensifies with depth as vertical stress accumulates, resulting in increasingly significant concentration differences between the upper, middle, and lower layers. In con  
Figure 27: Horizontal displacement along horizontal cut line at \(z=1.5\) m over time for varying Poisson ratios. Blue lines represent **Case 1**; black lines represent **Case 8**; red lines represent **Case 9**. trast, with a larger Poisson ratio, solute migration is slower, leading to generally lower concentrations across all depths. Mechanistically, Poisson's ratio influences solute transport by altering pore water pressure, consolidation rates, and migration pathways. A smaller Poisson ratio restricts lateral deformation, leading to concentrated vertical stress and rapid pore volume reduction, which significantly increases pore water pressure and enhances the hydraulic gradient driving solute migration. This results in faster, vertically focused solute movement, with pronounced concentration gradients and notable accumulation in the short term. The variation in Poisson's ratio primarily affects the concentration distribution in the center region, while its influence on the extent of outward diffusion and the concentration gradient is relatively small (Figure 30). A lower Poisson ratio (**Case 8**) significantly enhances the accumulation effect of solute concentration in the center region, whereas a higher Poisson ratio (**Case 9**) reduces the center concentration and slightly accelerates lateral diffusion. This indicates that Poisson's ratio indirectly influences the distribution characteristics of solutes in the center region by regulating the soil's lateral deformation capacity, while its impact on the overall diffusion pattern remains relatively weak.