## 4 Results and Discussion
### Spring-Thawing Clogging Model of OGFC Based on the Mistcherlich Growth Model  
After calculation, spring-thawing clogging model of three mixtures and model parameters are summarized in Table 11 and Figure 12.  
It can be seen from Table 11 that the determinant coefficient of each model is above 0.98, which indicates that the spring-thawing clogging model of the three mixtures has a higher prediction accuracy, and employing the Mistcherlich growth model is reasonable to describe the clogging process of the permeable asphalt pavement during the spring-thawing season. SBS-OGFC has the highest \(a\) value among the three mixtures, which indicates that the maximum degree of clogging of SBS-OGFC is the largest among the three mixtures. This is due to the higher porosity of the SBS-OGFC, which is consistent with the above data. The sequence of the clogging rate (index \(c\)) of the three asphalt mixtures during the spring-thawing season was OGFC \(>\) SBS-OGFC \(>\) COF-OGFC, respectively, which indicated that COF-OGFC not only has better pavement performance, but also has better permeability and resistance to rapid clogging behavior in the spring-thawing season. This may be due to the fact that oil shale waste adsorbs a large amount free asphalt, which reduces the probability that redundant asphalt blocks the effective pores, meaning that the generated pores are uniformly dispersed in the mixtures. It can be seen from Figure 12 that there is a significant difference in the maximum degree of clogging and clogging rate of the three permeable asphalt pavements under the summer clogging procedure. The OGFC has the largest maximum degree of clogging and the lowest clogging rate among the three mixes under the summer clogging procedure. This may be due to the OGFC having the smallest porosity, and the particle size of the clogging materials that can enter the interior of pavement is also relatively small, which reduces the probability that effective pores are directly blocked, and increases the possibility of deposition blockage. Thus, the clogging rate of OGFC is small and the maximum degree of clogging is large. It also can be concluded that the maximum clogging degree of permeable pavement in summer is greater than that in spring, and the clogging rate in summer is much smaller than that in spring. This indicates that there is an essential difference in the clogging behavior of the permeable pavement \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Season** & **Type** & **Fitting Equation** & **a** & **b** & **c** & **R2** \\ \hline \multirow{3}{*}{Spring} & OGFC & \(\text{y}(\text{t})=42.883-42.444e^{-0.185t}\) & 42.883 & 42.444 & 0.185 & 0.980 \\  & SBS-OGFC & \(\text{y}(\text{t})=51.398-50.681e^{-0.156t}\) & 51.398 & 50.681 & 0.156 & 0.990 \\  & COF-OGFC & \(\text{y}(\text{t})=45.303-45.064e^{-0.135t}\) & 45.303 & 45.064 & 0.135 & 0.996 \\ \hline \multirow{3}{*}{Summer} & OGFC & \(\text{y}(\text{t})=79.209-79.754e^{-0.015t}\) & 79.209 & 79.754 & 0.015 & 0.976 \\  & SBS-OGFC & \(\text{y}(\text{t})=56.452-56.926e^{-0.028t}\) & 56.452 & 56.926 & 0.028 & 0.997 \\ \cline{1-1}  & COF-OGFC & \(\text{y}(\text{t})=60.163-60.836e^{-0.023t}\) & 60.163 & 60.836 & 0.023 & 0.996 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Spring-thawing clogging model and model parameters of three mixtures. Figure 12: Clogging parameters of three mixtures in summer and spring season. (**a**) Maximum degree of clogging; (**b**) Clogging rate. in spring and summer. The maximum clogging degree of the permeable pavement in summer is about 40% higher than that in spring season, while the clogging rate is much lower than that in spring, at only about 14%, which indicates that the clogging behavior of the permeable asphalt pavement in spring is mostly in the rapid clogging mode, and that in summer is mostly in a slow deposition clogging mode.