## 2 Materials and Methods
### Material  
As presented in Figure 1a, Zhanjiang City is located in the southeast coastal area of Guangdong Province, China. The city's economy is in a stage of rapid development, and infrastructure construction is also proceeding rapidly.  
The clay samples were obtained from a coastal site in Zhanjiang City, with a sampling depth of 10-12 m. The specific location of sampling site is shown in Figure 1b. Zhanjiang clay is an interactive marine and terrestrial deposit. The detailed physical properties and grain size distribution of Zhanjiang clay are shown in Table 1. Zhanjiang clay exhibits a high water content and void ratio. Table 2 summarizes the basic mechanical properties of Zhanjiang clay.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \begin{tabular}{c} **Sampling** \\ **Depth (m)** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Natural** \\ **Ooisture** \\ **Content** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Liquid** \\ **Content** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **Plastic** \\ **Limit (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Hydraulic** \\ **Conductiv-** \\ **Limit (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Grain Size Distribution** \\ **Conductivity** \\ \end{tabular} \\ \cline{2-7}  & 10–12 & 1.75 & 1.45 & 54.92 & 62.2 & 28.8 & 2.7 \(\times\) 10\({}^{-8}\) & 59.1 & 40.9 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical properties and grain size distribution of Zhanjiang clay.  
Figure 1: Sampling site of Zhanjiang clay: (**a**) location of Zhanjiang; (**b**) location of sampling site.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{tabular}{c} **Overburden Pressure** \\ **(kPa)** \\ \end{tabular} & \begin{tabular}{c} **Yield Stress (kPa)** \\ \end{tabular} & \begin{tabular}{c} **Unconfined** \\ **Compressive Strength** \\ **of Undisturbed Clay** \\ **(kPa)** \\ \end{tabular} & \begin{tabular}{c} **Unconfined** \\ **Compressive Strength** \\ **of Remolded Clay** \\ **(kPa)** \\ \end{tabular} & \
\begin{tabular}{c} **Consitivity** \\ **Sensitivity** \\ \end{tabular} \\ \hline \hline
\begin{tabular}{c} 200 \\ \end{tabular} & 350 & \(110.6\) & 17.2 & 6.4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mechanical properties of Zhanjiang clay.  
As mentioned in the previous section, yield stress \(\sigma_{yield}\) is an important mechanical index for structured clay. [PERSON] et al. (2018) suggested that the yield stress \(\sigma_{yield}\) should be determined from the one dimensional compression curve of undisturbed specimen in the \(\log(e{+}1)-\log(\sigma^{\prime}{{}_{\rm{\it{v}}}})\) plot, where \(e\) is the void ratio of specimen, and \(\sigma^{\prime}{{}_{\rm{\it{v}}}}\) is the effective vertical stress applied in the tests. As illustrated in Figure 2, the average value of \(\sigma_{yield}\) for the undisturbed clay samples deduced from the two compression tests is approximately 350 kPa, whereas the overburden pressure of the clay samples is approximately 200 kPa, implying that the yield stress and the overburden pressure differ significantly.  
Figure 3 shows that the average value of unconfined compressive strength of undisturbed clay is 110.6 kPa, whereas that of remolded clay is only 17.2 kPa. Therefore, the sensitivity value of Zhanjiang clay is approximately 6.4. Based on the classification of [PERSON] (2018), clays with a sensitivity value greater than 4 are classed as very sensitive. Therefore, Zhanjiang clay is classed as very sensitive clay. The undisturbed clay has a high unconfined compressive strength, even though its physical properties are relatively poor for engineering application (Table 1). The high yield stress and high sensitivity of Zhanjiang clay are primarily due to its strong structure that stems primarily from the natural cementation of free iron oxides (Zhanjiang, 2018; Zhanjiang, 2018).