## 3 Reference Case Study
### Tests and Physical Parameters
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & \multirow{2}{*}{**Name**} & \multirow{2}{*}{**Thickness/m**} & \multirow{2}{*}{**Natural Density /(kN\(\cdot\)m\({}^{-3}\))**} & \multirow{2}{*}{**Volume Water Content /\%**} & \multirow{2}{*}{**Void Ratio**} & \multirow{2}{*}{**Initial Permeability /(ccm\(\cdot\)s\({}^{-1}\))**} & \multirow{2}{*}{**C\({}_{\textbf{u}}\)1**} & \multirow{2}{*}{**C\({}_{\textbf{c}}\)2**} \\  & & & & & & & & \\ \hline \multirow{2}{*}{I\({}_{1}\)} & Artificial & \multirow{2}{*}{4.8} & \multirow{2}{*}{15.1} & \multirow{2}{*}{44.2} & \multirow{2}{*}{1.01} & \multirow{2}{*}{8.9 \(\times\) 10\({}^{-3}\)} & \multirow{2}{*}{7.9} & \multirow{2}{*}{1.4} \\  & fill-1 & & & & & & & \\ \hline \multirow{2}{*}{I\({}_{2}\)} & Artificial & \multirow{2}{*}{4.5} & \multirow{2}{*}{16.9} & \multirow{2}{*}{41.7} & \multirow{2}{*}{0.97} & \multirow{2}{*}{4.8 \(\times\) 10\({}^{-3}\)} & \multirow{2}{*}{7.1} & \multirow{2}{*}{1.5} \\  & fill-2 & & & & & & & \\ \hline \multirow{2}{*}{II} & Sandy & \multirow{2}{*}{7.3} & \multirow{2}{*}{17.6} & \multirow{2}{*}{38.3} & \multirow{2}{*}{1.12} & \multirow{2}{*}{3.7 \(\times\) 10\({}^{-3}\)} & \multirow{2}{*}{9.5} & \multirow{2}{*}{1.7} \\  & gravel & & & & & & & \\ \hline \multirow{2}{*}{III} & Pelitic & \multirow{2}{*}{\(\succ\)7} & \multirow{2}{*}{20.3} & \multirow{2}{*}{/} & \multirow{2}{*}{/} & \multirow{2}{*}{/} & \multirow{2}{*}{/} & \multirow{2}{*}{/} \\  & siltstone & & & & & & & \\ \hline \hline \end{tabular}  
\({}^{1}\) Cu: coefficient of uniformity; 2 C: Curvature coefficient.  
\end{table} 
Table 1: Physical and mechanical indexes of soil layer in the typical section. Figure 4: The geological cross section of typical section. Artificial fill soil samples were taken along the section height at the ancient riverbank for soil test, and soil samples with a particle size of less than 2 mm for particle analysis were taken after screening. The grain grading curves of layers I and II soil samples less than 2 mm are shown in Figure 6. The mass of the soil samples in layers I and II with particle size greater than 0.075 mm should not exceed 50% of the total mass, the liquid limit was 44%, the plastic limit was 27%, the plastic index was 17, and the filling type was silty clay. The porous clay plate test was used to measure the pore water pressure of the saturated-unsaturated soil mass of I\({}_{1}\), I\({}_{2}\) and II, as shown in Figure 6. The relationship between  
Figure 5: Soil property test. (**a**) Sieving soil samples; (**b**) sub packaging of soil particles; (**c**) laser particle analysis test; (**d**) remodeling soil preparation; (**e**) measuring the relationship between permeability coefficient and matric suction; (**f**) scanning soil using electron microscope. Figure 6: Fine particle grading curve of soil sample. the water content and the matric suction was made available by fitting the test data. The relationship curve between the permeability coefficient and the matric suction was obtained using the van Genuchten model, as shown in Figure 7.  
Figure 7b shows the relationships between the permeability coefficient and matric suction in the I\({}_{1}\), I\({}_{2}\) and II soil samples. The permeability coefficients of saturated soil are constants, and the relationship between the permeability coefficient and suction of unsaturated soil is generalized as a linear relationship, as shown by the dotted lines 1, 2 and 3 in Figure 7b, and Equation (10) are their expressions. The hydraulic gradient of the saturated soil is calculated with Equation (9), and the hydraulic gradient of unsaturated soil is calculated with Equation (12). The relevant parameters and calculation formulas are shown in Table 2.  
The soil samples before and after the porous clay plate test were taken, dried and then subjected to the scanning electron microscope test.