# Effects of Freeze-thaw Cycles on the Mechanical Properties and Microstructure of a Dispersed Soil
## 2 Materials and Methods
### Specimen Preparation  
The methodology employed for sample preparation in this investigation is illustrated in Figure 2a. Dispersed soil samples were collected and subjected to air drying. The dried soil specimens were communicated and sieved through a 2 mm mesh to eliminate oversized particles. In this study, the specimens were analyzed and determined using a compaction degree of 95%. The soil-water mixture was enclosed within a self-sealing bag and allowed to incubate at a temperature of 20 \({}^{\circ}\)C for a duration of 24 h, ensuring uniform water distribution within the soil specimens. Following this, the soil samples were transferred  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Property** & **Values** \\ \hline Sand group (2–0.075 mm) & 15.90\% \\ Silt group (0.075–0.005 mm) & 63.33\% \\ Clay group (\textless{}0.005 mm) & 20.77\% \\ Soil type information & lean clay (CL) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Particle size composition properties of dispersed soil in the study area.  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Property** & **Values** \\ \hline Liquid limit & 38.79\% \\ Plastic limit & 18.59\% \\ Plasticity index & 20.20 \\ Optimum water content & 16.76\% \\ Maximum dry density & 1.730 g/cm\({}^{3}\) \\ pH & 9.27 \\ Dispersion (from double hydrometer test) & 88.18\% \\ SAR & 53.68 \\ Total soluble salt content & 0.146\% \\ Na\({}^{+}\) & 24.89 mmol/kg \\ HCO\({}_{3}\)\({}^{-}\) & 18.71 mmol/kg \\ CO\({}_{3}\)\({}^{2-}\) & 2.60 mmol/kg \\ Ca\({}^{2+}\) & 0.28 mmol/kg \\ Mg\({}^{2+}\) & 0.15 mmol/kg \\ K\({}^{+}\) & 0.12 mmol/kg \\ \hline \hline \end{tabular}
\end{table}
Table 2: Physical properties and soluble salt content of dispersed soil in the study area.  
Figure 1: Basic location map of the sampling location in Qian’an, Jilin Province. (**a**) Geographical location of Qian’an, Jilin Province, and (**b**) satellite photographs corresponding to the sampling site.  
into a sample-making mold and compressed under static pressure to obtain remolded soil samples of a desired size. Two sizes of remolded dispersed soil samples were prepared, ring knife specimens (\(\Phi\) 61.8 mm \(\times\) 20 mm) and cylindrical specimens (\(\Phi\) 39.1 mm \(\times\) 80 mm), as subsequent mechanical tests were required for further study. The remolded soil samples that were prepared underwent sealing with plastic wrap and were subsequently positioned within self-sealing bags to mitigate the potential for moisture evaporation. Changes in specimen volumes were limited using external devices. The remolded soil samples sealed with cling film were frozen in a freeze-thaw cycle chamber for 12 h to ensure complete freezing, and then the samples were taken out and thawed at room temperature for 12 h. This process constituted an entire freeze-thaw cycle. The aforementioned procedure was iterated to procure soil samples that had experienced varying numbers of freeze-thaw cycles for further investigations. This study divided the freeze-thaw cycles into eight stages: an initial state and the 1 st, 3 rd, 5 th, 7 th, 9 th, 12 th, and 15 th cycles.