## 5 Numerical Simulation of Temperature Field of Pemafrost Subgrade
### Analysis of Temperature Field Simulation Results for Frozen Road
It can be concluded that the rate of decline of the permafrost table in this section has been gradually slowing down, indicating that the temperature of the soil in the lower part of the subgrade has increased under the influence of the temperature of the upper boundary, but the trend of growth has been gradually decreasing. This results in a gradual slowing down of the rate of decrease in the permafrost table for all the years in this section, indicating that the temperature of the soil in the lower part of the subgrade has increased under the influence of the temperature of the upper boundary, but the trend of increase is gradually decreasing. The permafrost table in the lower part of the medial divider decreased at the fastest rate, and the lower part of the permafrost table at the right toe of the slope decreased at a significantly faster rate than that at the left toe of the slope. This phenomenon occurs because the sunny-shady slope effect accelerates the degradation of the permafrost in the lower part of the right toe of the slope. The simulated temperature data in October of year five at different locations were extracted, and the simulation results were compared with the measured data in October 2023. Plot the curves as shown in Figure 10. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time** & **Medial Divider** & **Left Toe of the Slope** & **Right Toe of the Slope** & **Natural Ground Surface** \\ \hline Year 1 & \(-\)5.02 m & \(-\)2.06 m & \(-\)4.52 m & \(-\)4.04 m \\ Year 5 & \(-\)7.57 m & \(-\)4.65 m & \(-\)7.47 m & \(-\)4.96 m \\ Year 10 & \(-\)9.49 m & \(-\)5.98 m & \(-\)9.09 m & \(-\)5.71 m \\ Year 15 & \(-\)10.78 m & \(-\)6.67 m & \(-\)10.11 m & \(-\)6.23 m \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Permafrost table at different locations on the subgrade. As can be seen from Figure 9 above, the simulation results of shallow soil temperature at each location are larger than the measured data. The location of 0 \({}^{\circ}\)C is lower than the actual location, especially in the medial divider, and the right toe of the slope is more obvious. The main reason for this phenomenon is that the Shi-La highway has been open to traffic since 2016 after delivery, and data monitoring began in 2020. During the data monitoring period, the amount of subgrade settlement is large, and the thickness of pavement repair in the medial divider location reaches 152 cm, which reduces the accuracy of the measured data. The simulation results are one year later than the measured data, during which time soil temperatures may have risen further and the permafrost table may have fallen further. The moisture field was not well coupled in the simulation process, thus affecting the coupling results of the temperature field. There is a gap between the various physical parameters of the soil used in the simulation process and the actual conditions in the field. In general, the simulation results and the measured data have roughly the same trend: with the increase in depth, the soil temperature gradually decreases and finally tends to stabilize.