## 3 Results
### Microscopic Evolutionary Properties of Hipparion Laterite Under F-T Effect
The changes in porosity and the percentage of each type of pore are summarized in Table 4.  
The combined effects of F-T cycles and moisture content disrupt the soil's original structure, leading to particle rearrangement and changes in pore orientation. The pore orientation angle, calculated using Equation (6), represents the angle between the pore's long axis and the positive x-axis. To analyze the pore orientation distribution, the range from 0\({}^{\circ}\) to 180\({}^{\circ}\) was divided into 18 intervals. The orientation frequency of each interval is determined by the percentage of pores within that range. The orientation frequency of pores is calculated and expressed by Equation (7) as follows:  
\[\alpha^{\prime}=\left\{\begin{array}{l}90^{\circ}-\alpha,\ \alpha<90^{  
\[F(\alpha^{\prime})=\frac{n\alpha^{\prime}}{n}\times 100\% \tag{7}\]  
In the equation, \(\alpha\) represents the pore orientation angle, defined as the angle between the major axis of a pore and the horizontal direction; \(\alpha^{\prime}\) denotes the adjusted pore orientation angle, derived through transformation scenarios 1, 2, and 3; \(F(\alpha^{\prime})\) signifies the orientation frequency, where \(n_{\alpha^{\prime}}\) corresponds to the number of pores within a specific orientation interval of \(\alpha^{\prime}\), and \(n\) is the total number of pores in the analyzed region. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Moisture** & \multicolumn{4}{c}{**16\%**} \\ \hline
**F-T-C** & **A** & **B** & **C** & **D** & **Porosity** \\ \hline
0 & 0.38\% & 3.02\% & 55.50\% & 41.10\% & 0.1417 \\
2 & 0.54\% & 4.30\% & 59.51\% & 35.65\% & 0.1574 \\
4 & 1.26\% & 4.48\% & 58.85\% & 35.41\% & 0.1671 \\
6 & 1.89\% & 5.14\% & 59.41\% & 33.57\% & 0.1787 \\
8 & 2.10\% & 7.63\% & 59.90\% & 30.37\% & 0.1909 \\
10 & 2.68\% & 9.09\% & 61.35\% & 26.88\% & 0.2103 \\ \hline  & \multicolumn{4}{c}{**20\%**} \\ \hline
0 & 0.43\% & 3.75\% & 57.18\% & 38.64\% & 0.1631 \\
2 & 0.62\% & 4.32\% & 57.91\% & 37.15\% & 0.1733 \\
4 & 1.57\% & 6.55\% & 57.10\% & 34.78\% & 0.2022 \\
6 & 2.21\% & 7.28\% & 60.19\% & 30.32\% & 0.2382 \\
8 & 2.87\% & 8.25\% & 62.36\% & 26.52\% & 0.2728 \\
10 & 3.26\% & 10.48\% & 62.69\% & 23.57\% & 0.2871 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Porosity and pore percentage of soil under F-T and water coupling effects. Figure 14: Variation in pore size distribution and apparent porosity of samples. According to Figure 15a,b, Hipparion laterite specimens with a low moisture content (16% and 24%) exhibit a more uniform degree of pore orientation in their unfrozen and thawed state. For specimens with 24% moisture content, the pore orientation angle was concentrated between 120\({}^{\circ}\) and 150\({}^{\circ}\). After two F-T cycles, the low-moisture specimens exhibited a shift towards a 0-10\({}^{\circ}\) orientation, while the high-moisture specimens shifted to 60-110\({}^{\circ}\). After 4 and 6 F-T cycles, the pore orientation angles for all moisture content specimens were concentrated in the near-vertical range of 70\({}^{\circ}\)-100\({}^{\circ}\) (Figure 15c,d. As the F-T effect intensifies, the pore orientation angle is redistributed, gradually reaching equilibrium and stabilization after 8 and 10 cycles (Figure 15e,f, accompanied by a significant weakening of the pore orientation. Figure 15: The relationship between the directional frequency of the pore and the number of F-T cycles. (**a–f**) denotes 0 to 10 cycles. Overall, the degree of pore orientation is a complex process influenced by moisture content and F-T cycles [17; 18]. The probabilistic entropy and oriented fractal dimension serve as tools to visualize and quantify the orderliness of the pore orientation.