## 2 Materials and Methods
### Test Procedure  
#### 2.3.1 Saturated and Unsaturated Infiltration Procedures  
In this study, the variable hydraulic head method was used to carry out saturated infiltration tests on remolded soil samples with different dry densities using a TST-55 (Nanjing Soil Instrument Factory Co., Nanjing, China) permeameter (Table 3). Figure 2 shows a diagram illustrating the silt column and the positioning of the sensors employed to monitor the moisture content and progression of the wetting front. The key elements of the setup include an acrylic cylinder, ceramic cups, moisture content sensors, and a rainfall system. The cylindrical infiltration device has an inner diameter of 13 cm and a height of 100 cm, is made of transparent acrylic with a thickness of 3 mm, and has a graduated label paper to facilitate the measurement of the advancing displacement of the wetting peak. A flanged air-permeable bottom plate is fixed at the bottom to drain the rainwater that passes through the infiltration layer and prevent the occurrence of water accumulation in the saturated bottom soil layer, thus preventing abnormal moisture content in the lower soil layer. In his book Unsaturated Soil Mechanics, [PERSON] mentioned that the spacing between probes for moisture content and suction should be 10% of the entire soil column length [25]. Therefore, the acrylic columns were equipped with moisture content (MC) sensors at 5 cm intervals, starting from the base of the silt column. Initially, a 10 cm thick layer of gravel was positioned at the bottom of the acrylic cylinder and covered with a nonwoven geotextile. The large pores between gravel stones are conducive to the drainage of soil pore gases and prevent the soil particles from being washed out from the bottom by water. In the experiment, the soil column was prepared by layered compaction and was \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline Oxide Mass Wt (\%) & SiO\({}_{2}\) & A1\({}_{2}\)O\({}_{3}\) & CaO & Fe\({}_{2}\)O\({}_{3}\) & MgO & K\({}_{2}\)O & Na\({}_{2}\)O & TiO\({}_{2}\) & P\({}_{2}\)O\({}_{5}\) & MnO \\ \hline \multirow{4}{*}{XRF results} & CH & 56.85 & 15.15 & 13.51 & 5.44 & 3.51 & 2.88 & 1.26 & 0.76 & 0.20 & 0.11 \\  & QY & 59.72 & 14.50 & 11.77 & 4.68 & 3.51 & 2.70 & 1.79 & 0.71 & 0.21 & 0.10 \\  & YA & 59.47 & 14.72 & 11.82 & 5.07 & 3.21 & 2.79 & 1.59 & 0.72 & 0.20 & 0.10 \\  & LL & 58.41 & 14.90 & 13.32 & 5.65 & 3.19 & 2.81 & 1.65 & 0.71 & 0.22 & 0.11 \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Normalized \\ mass percent (\%) \\ LL \\ \end{tabular} } & CH & 51.95 & 13.53 & 15.57 & 7.14 & 4.67 & 4.01 & 2.08 & 0.84 & 0.21 & 100\% \\  & QY & 51.33 & 15.42 & 14.13 & 6.92 & 4.50 & 3.69 & 3.08 & 0.77 & 0.17 & 100\% \\  & YA & 51.93 & 15.79 & 14.55 & 6.63 & 3.62 & 2.20 & 4.32 & 0.80 & 0.15 & 100\% \\  & LL & 50.52 & 15.15 & 15.34 & 6.95 & 3.42 & 3.66 & 3.95 & 0.80 & 0.22 & 100\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical composition of the test materials. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Samples** & & & \multicolumn{4}{c}{**Density (g/cm\({}^{3}\))**} \\ \hline CH soil & 1.45 & 1.52 & 1.60 & 1.67 & & & \\ QY soil & 1.45 & 1.57 & 1.63 & 1.72 & & & \\ YA soil & 1.31 & 1.39 & 1.47 & 1.50 & 1.55 & 1.60 & 1.70 \\ LL soil & 1.45 & 1.50 & 1.57 & 1.65 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Design of the saturated infiltration experiments. then covered with fine sand, a stack of filter paper and permeable stones. The permeable stones and filter paper could evenly distribute the infiltration water across a cross-section of the soil column. Fine sand acts as a transition medium for surface infiltration water flow to ensure the uniformity of water flow distribution in the infiltration cross-section and to prevent the infiltration water flow from scouring or destroying the surface soil layer, so as to ensure normal infiltration. After the soil column was formed, the pore pressure dissipated after standing for 24 h, which effectively reduced the experimental error.