## 3 Results and Discussion  
### Temperature Field Analysis of BRT Asphalt Pavement Structure  
Equations (7) and (8) constitute the model for predicting daily maximum temperature and daily minimum temperature at a given depth of asphalt pavement. This model was proposed by [PERSON] [48] and has wide applicability. To verify the reliability of the temperature field model, the calculated daily maximum and minimum temperature in this study were compared to predicted temperatures obtained with Equations (7) and (8). In the process of obtaining the predicted temperature, \(T_{\rm{amax}}\) and \(T_{\rm{amin}}\), derived from Table 3, were 33.6 \({}^{\circ}\)C and 20.8 \({}^{\circ}\)C, respectively; \(T_{\rm{m}}\) was 23.6 \({}^{\circ}\)C, which was the average monthly temperature of the hottest months of the last 10 years in Lanzhou. The calculated and predicted temperatures are listed in Table 6.  
\[T_{\rm{pmax}}= 3.040+0.994T_{\rm{amax}}-0.007T_{\rm{amax}}\cdot H-1.676H+0.201H^ {2}-0.008H^{3}+0.498T_{\rm{m}} \tag{7}\] \[(R=0.972)\]  
\[T_{\rm{pman}}=-3.399+0.721T_{\rm{amin}}+0.377H-0.010H^{2}+0.488T_{\rm{m}}\ (R=0.990) \tag{8}\]  
where \(T_{\rm{pman}}\) denotes the daily maximum temperature at the given depth of asphalt pavement (\({}^{\circ}\)C); \(T_{\rm{pman}}\) denotes the daily minimum temperature at the given depth of asphalt pavement (\({}^{\circ}\)C); \(T_{\rm{amax}}\) denotes daily maximum air temperature (\({}^{\circ}\)C); \(T_{\rm{amin}}\) denotes daily minimum air temperature (\({}^{\circ}\)C); \(H\) denotes the depth below surface (cm); and \(T_{\rm{m}}\) denotes the mean monthly temperature over the calendar year.  
As shown in Table 6, with the increase in asphalt pavement depth, the calculated temperature and the predicted temperature basically exhibited the same trend, namely, the daily maximum temperature decreased and the daily minimum temperature increased. Moreover, the difference between the calculated temperature and the predicted temperature at the same depth was relatively small. Notably, the maximum difference was 3.5 \({}^{\circ}\)C, which had little influence on the mechanical properties of asphalt pavement. In conclusion, the temperature field model established above is highly reliable, and the calculation results satisfy our analysis needs.  
Figure 6 shows the temperature change of the BRT asphalt pavement structure during 24 h of 1 day. As shown in Figure 4, the temperature change trend of the pavement structure was roughly the same as that of air, and the temperature change of the pavement surface was basically synchronized with that of the air temperature over time. Because the rate of absorption of solar radiation of the asphalt pavement was far greater than that of the atmosphere, the temperatures of the upper, intermediate and lower surface layers were obviously higher than that of the atmosphere. With increasing depth of the pavement structure, the change in temperature gradually lagged, and the range of the temperature rise gradually decreased. The upper, intermediate and lower surface layers sequentially reached maximum temperature values of approximately 51.7 \({}^{\circ}\)C at 14:00, 45.0 \({}^{\circ}\)C at 14:30 and 39.0 \({}^{\circ}\)C at 16:00. The influence of atmospheric temperature change on the structural layers below the base was not obvious.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{
\begin{tabular}{c} **Depth below** \\ **Surface (cm)** \\ \end{tabular} } & \multicolumn{2}{c}{**Daily Maximum Temperature (\({}^{\circ}\)C)**} & \multicolumn{2}{c}{**Daily Minimum Temperature (\({}^{\circ}\)C)**} \\ \cline{2-5}  & **Calculated** & **Predicted** & **Calculated** & **Predicted** \\  & **Temperature** & **Temperature** & **Temperature** & **Temperature** \\ \hline
0 & 51.7 & 48.2 & 22.0 & 23.1 \\
4 & 45.0 & 43.2 & 22.5 & 24.5 \\
9 & 39.0 & 41.4 & 23.0 & 25.7 \\
16 & 33.4 & 36.3 & 23.4 & 26.6 \\ \hline \end{tabular}
\end{table}
Table 6: Comparison of calculated and predicted temperatures of asphalt pavement.