## 3 Results and Discussion  
### Temperature Stress of Pavement Under Typical Temperature Conditions  
Based on the measured data from a meteorological station along the highway, the large temperature difference in spring and fall and the extreme low temperature difference in winter were selected as typical continuous variable temperature environments. Figure 9 shows the variation of air temperature and solar radiation over a 24 h period under different seasons in the region. According to the asphalt pavement temperature field theory [27; 28; 29], a combination of solar radiation, air temperature, convective heat exchange, and effective radiation from the pavement is used to realize the temperature field simulation. The temperature changes in each structural layer of the pavement for 1 day under spring, fall, and winter temperature differences are shown in Figure 10.  
Figure 8: Restart analysis flowchart. Figure 9: Changes in air temperature and solar radiation under typical temperature differences. From the figure, it can be seen that the temperature change trend of each structural layer under the three temperature difference conditions is basically the same. The magnitude of change in each structural layer decreases with depth. The magnitude of change in the surface layer was significant, while the base layer and below remained essentially stable. In addition, it can be seen that the pavement temperature field in the fall is mainly characterized by heat dissipation from the interior to the exterior. The internal temperature of the pavement structure reaches a minimum in winter and then exhibits heat absorption from the outside in spring. The temperature gradient along the depth direction undergoes a change from negative to positive to negative over the course of the day. The temperature gradient was close to zero from 8:00 to 10:00 and reached a maximum by about 14:00 in the afternoon. The temperature gradient again approached 0 at -18:00-22:00 p.m. The negative temperature gradient gradually increased and reached its maximum at -5:00-6:00 a.m. The maximum positive temperature gradient was 90.62 \({}^{\circ}\)C/m, and the maximum negative temperature gradient was 68.54 \({}^{\circ}\)C/m. Both positive and negative temperature gradients reached their maximum in winter. By introducing the temperature field into the mechanical model, the temperature stresses induced by different temperature differences in each structural layer of the pavement can be obtained. When temperature is a single factor, temperature stresses are mainly  
Figure 10: Temperature changes in each structural layer of the pavement. manifested as horizontal transverse tensile stresses in the pavement. And when the generated transverse tensile stress is greater than the ultimate tensile strength of the material, transverse cracks will be generated, extended, and expanded. The distribution patterns of tensile stresses in each structural layer of the pavement under continuous temperature change in spring, fall, and winter are shown in Figure 10.  
As can be seen from Figure 11, the temperature stresses in each structural layer show a regular variation. Spring and fall seasons show alternating tensile and compressive stresses, and winter seasons show complete tension with little effect of temperature stresses at the base. In terms of daily variation, the road surface temperature stress reached its maximum value at 6:00 in all three seasons, and the maximum compressive stress appeared at 15:00. Combined with Figure 9, it can also be seen that the road surface temperature extremes and temperature stress extremes exhibit the same pattern of change. And the peak temperature and the peak stress appear to be lagged sequentially with depth, and the greater the depth, the longer the lag time. And the longer the lag time of the peak temperature stress is compared to the peak temperature with increasing depth. Figure 11: Temperature stress distribution in each structural layer of the pavement.