## 5 Rutting Prediction Model and Parameter Values of China's Asphalt Pavement  
The rutting performance prediction model in China's Specifications is established by the cumulative permanent deformation. First, each asphalt mixture layer is layered, and then according to the rutting test under standard conditions, the rutting permanent deformation of each layer of asphalt mixture is obtained, and the permanent deformation of each layer and the total permanent deformation of the asphalt mixture layer are calculated, so as to achieve the purpose of controlling the structure design. The rutting performance prediction model expressions are shown in Equations (2) and (3).  
Figure 4: Axle load and axial distribution of trucks in loading mode II.  
Figure 5: Curves of the cumulative number of equivalent single-axle loads.  
Figure 3: Axle load and axial distribution of trucks in loading mode I.  
\[R_{a}=\sum_{i=1}^{n}R_{ai} \tag{2}\]  
\[R_{ai}=2.31\times 10^{-8}k_{Ri}T_{pef}^{2.93}p_{i}^{1.80}N_{e}^{0.48}R_{0i} \tag{3}\]  
where \(R_{a}\) is the permanent deformation of the asphalt mixture layer (mm); \(R_{ai}\) is the permanent deformation of the \(i\)-th layer (mm); \(R_{0i}\) is the permanent deformation of the \(i\)-th layer of the asphalt mixture in the laboratory rutting test at 60 \({}^{\circ}\)C (mm); \(N_{e}\) is the cumulative number of ESALs; \(T_{pef}\) is the rutting equivalent temperature of the asphalt mixture layer (\({}^{\circ}\)C); \(p_{i}\) is the vertical compressive stress on the top surface of the \(i\)-th layer (MPa); \(k_{Ri}\) is the comprehensive correction coefficient, calculated according to Equations (4)-(6); \(z_{i}\) is the depth (mm) from the midpoint of the \(i\)-th layer to the road surface; and \(h_{a}\) is the thickness of the asphalt mixture layer (mm); when it is greater than 200 mm, take 200 mm.  
\[k_{Ri}=(d_{1}+d_{2}.z_{i}).0.9731^{z_{i}} \tag{4}\]  
\[d_{1}=-1.35\times 10^{-4}h_{a}^{2}+8.18\times 10^{-2}h_{a}-14.50 \tag{5}\]  
\[d_{2}=8.78\times 10^{-7}h_{a}^{2}-1.50\times 10^{-3}h_{a}+0.90 \tag{6}\]  
Since the long-term evolution data of rutting in this research is obtained based on the RIOHTrack full-scale pavement test track, the traffic loads on each pavement structure are exactly the same, so the \(N_{e}\) of each structure should take the same value for rutting prediction, which can be taken according to Equation (1) and Figure 5.  
According to the regulations in China's Specifications, \(T_{pef}\) is related to the temperature in the region where the pavement structure is located and the thickness of the asphalt mixture layer. It can be seen from the calculation that for the STR1, STR2, STR4, and STR5 in this research, the equivalent temperature of the rutting is 22.02 \({}^{\circ}\)C; the equivalent temperature of rutting of STR7 and STR8 is 22.98 \({}^{\circ}\)C; and the equivalent temperature of rutting of STR10, STR12, STR11, STR13, STR16, STR17, STR18, and STR19 is 23.30 \({}^{\circ}\)C.  
There are 10 kinds of asphalt mixtures in the structures of this research. The test results of the permanent deformation of each asphalt mixture in the laboratory rutting test at 60 \({}^{\circ}\)C are shown in Table 1. The value of \(R_{0i}\) can be selected according to Table 1. In addition, \(p_{i}\) and \(k_{Ri}\) can be calculated according to the layered model of each pavement structure, and calculated according to the mechanics of the elastic layered system and Equations (4)-(6), and will not be repeated here.