## 4 Discussion
Consequently, the unconfined compressive strength exhibited a substantial growth rate in the initial period, a moderate growth rate in the intermediate period, and a significant growth rate in the later period as the temperature decreased. Figure 6: Trend of UCS with strain rate: (**a**) Clay. (**b**) Silty soil. (**c**) Sandy soil. decreased. This finding aligned with the research conducted by [PERSON] et al. [19] and [PERSON] et al. [50], confirming the generalizability of the model. Comparing the three different permafrost soils, pulverized soils exhibited the highest overall strength, followed by clays and sands. Fine-grained soils, such as clay and silt, contained a higher proportion of weakly bound water. As the temperature decreased, more weakly bound water froze, leading to increased soil cohesion and higher strength. However, the strongly bound water remained unfrozen but enveloped the soil particles, maintaining its ice cementation capacity. On the other hand, coarse-grained soils, represented by sandy soils, possessed a monogranular structure characterized by low densities and large interparticle pores. This weakened the ice cementation ability after the freezing of unfrozen water. Additionally, a significant amount of pore water remained unfrozen in these soils, resulting in an overall lower strength. The bonding pattern is illustrated in Figure 7.  
As depicted in Figure 6, the unconfined compressive strength of three permafrost types increased with an increase in the strain rate. The strength exhibited varying degrees of sensitivity to different strain rates, demonstrating stronger sensitivity within the S2 strain rate range, while exhibiting relatively minor variations within the S1 and S3 rate intervals. At a small strain rate (S1), although there was an increase in compressive strength, the overall increment was modest, indicating low sensitivity. Conversely, when the strain rate increased from \(10^{-4}\) s\({}^{-1}\) to \(10^{-3}\) s\({}^{-1}\) (S2), the rise in the compressive strength became significant. Moreover, the lower the temperature was, the more pronounced the increase and the higher the sensitivity. Consequently, the unconfined compressive strength of permafrost was higher at elevated strain rates and lower temperatures. It is important to note that at a temperature of \(-20\)\({}^{\circ}\)C, there was a tendency for the rate of strength increase to diminish when the strain rate increased from \(10^{-3}\) s\({}^{-1}\) to \(10^{-2}\) s\({}^{-1}\) (S3). This change could likely be attributed to the freezing of all free and weakly bonded water within the soil, resulting in a decrease in unfrozen water within the pore space of the densely compacted soil. As a result, the magnitude of the strength increase diminished. Earlier studies mostly focused on the physical properties of some single permafrost, this study was conducted by collecting a wide range of different data and analyzing them using XGB. A broader understanding of the strength properties of permafrost can be obtained through big data analysis. However, due to the prevalent lack of interpretability in machine learning, it fails to intuitively illustrate underlying physical mechanisms. Future research endeavors could overcome the limitations of purely data-driven methods by integrating physical information into computational models, such as employing physical information as constraints in data processing. This integration would aid in bridging the gap between data-driven methodologies and physical insights, enhancing the interpretability of the models used in permafrost analysis.