## 2 Materials and Methods
### Test Materials and Test Program
#### 2.2.2 Experiment Scheme  
According to the \"Standard for Geotechnical Test Methods\" (GB/T50123-2019), the test shear strain rate is 0.5%/min, that is, 0.4 mm/min, and the test is stopped when the shear strain is 20%. The instrument used in the test was an SY10-2 strain control triaxial instrument. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Extraction** & \multirow{2}{*}{\(d_{s}\) (g/cm\({}^{3}\))} & \(w\) (\%) & \(w_{1}\) (\%) & \(w_{p}\) (\%) & \(I_{p}\) (g/cm\({}^{3}\)) & \(\rho\) (g/cm\({}^{3}\)) & \(\rho\) (g/cm\({}^{3}\)) & \(\rho\) (g/cm\({}^{3}\)) \\ \hline
3.0 & 2.70 & 9.2 & 30.6 & 18.3 & 12.3 & 1.48 & 1.35 & 1.00 \\
4.0 & 2.70 & 11 & 27.6 & 16.8 & 10.8 & 1.57 & 1.41 & 0.92 \\
5.0 & 2.70 & 17 & 34.6 & 16.6 & 18 & 1.66 & 1.42 & 0.91 \\
6.0 & 2.70 & 16.6 & 28 & 17 & 11 & 1.59 & 1.36 & 0.92 \\
7.0 & 2.70 & 16.7 & 34.8 & 23.5 & 11.3 & 1.49 & 1.28 & 1.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Indicators of Loess Physical Properties. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Content of Different Particles (\%)**} \\ \hline
**Extraction** & \multirow{2}{*}{\
\begin{tabular}{c} **Clay Particle** \\ **(mm)** \\ **\textless{}0.005** \\ \end{tabular} } & **Silt Particle** & \multirow{2}{*}{
\begin{tabular}{c} **Sand Particle** \\ **(mm)** \\ **0.005–0.075** \\ \end{tabular} } & **Sand Particle** & \multirow{2}{*}{**Types of Soil**} \\
**3 m** & 18.97 & 80.28 & 0.75 & silty clay \\ \hline
5 m & 17.68 & 80.82 & 1.5 & silty clay \\ \hline
7 m & 19.8 & 77.35 & 2.85 & silty clay \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Grain Size Composition of Loess. In accordance with the \"Standard for Geotechnical Test Methods\" (GB/T50123-2019), the undisturbed soil blocks were cut into cylindrical soil samples (d = 39.1 mm, h = 80 mm) required for the test. The remolded soil samples were also made into the size of this specification. Prepare undisturbed and remolded soil samples with different moisture contents (6%, 11%, 16%, 21%, 26%, 31%, and 36%) to study the structural changes of loess with different moisture contents and the relationship between loess structure and loess moisture. The undisturbed saturated sample and remolded saturated sample were prepared by the vacuum saturation method, while other moisture content soil samples were prepared by the following methods. (1) Preparation method of undisturbed soil samples with different moisture contents  
To prepare undisturbed loess samples with different moisture contents and evenly distribute moisture in various parts of the soil, the \"water film transfer method\" and \"natural wind dry method\" were used to control the required initial moisture content of the samples. For samples with a target moisture content higher than the natural moisture content, the first step is extraction saturation. The quality of the sample when the target moisture content is reached is calculated by Formula (2), and then the sample is naturally air-dried to the target weight. For samples whose target moisture content is lower than the natural moisture content, the natural air-dried method is directly used to air dry them to the target quality, and the target quality is also calculated by Formula (2). Finally, the sample was sealed with plastic wrap and placed in a moisturizing cylinder for 3-5 days, and the test was carried out after the water inside the sample was evenly distributed. \[m_{t}=\frac{m_{o}}{1+0.01w_{o}}\times(1+0.01w_{1}) \tag{2}\]  
In Formula (2),  
\(m_{o}\): quality of natural moisture content samples (g),  
\(w_{o}\): natural moisture content of the sample (%),  
\(w_{1}\): target moisture content of the sample (%),  
\(m_{t}\): the quality of the sample when the target moisture content is reached (g).