## 4 Results and Discussion
### Permeability Quality Evaluation Test Results
the first eight spring clogging cycles, which is consistent with the declining trend of the permeability coefficient. This also indicated that the porosity of the permeable pavement has a significant correlation with the permeability coefficient. The largest decrease in the porosity of the the three asphalt mixtures was for SBS-OGFC. This is because SBS-OGFC has the largest porosity, and the probability of triggering the clogging behavior is much higher than for the other two mixtures. It can be seen from Figure 9b that the porosity of the three mixtures decreased with the increase of summer clogging cycles. After 40 summer cycles, the porosity of the three asphalt mixtures began to stabilize, which indicated that the clogging materials in the permeable asphalt mixture almost reached saturation. After 50 summer clogging cycles, the porosities of OGFC, SBS-OGFC, and COF-OGFC were 11%, 8.23%, and 9.69%, respectively, and after 20 spring clogging cycles, the porosities of OGFC, SBS-OGFC, and COF-OGFC were 10.34%, 8.27%, and 9.97%, respectively. This indicated that after 20 spring clogging cycles, or 50 summer clogging cycles, the clogging materials in the permeable asphalt pavement reached saturation, which means the \"End-of-Life\" of the permeable asphalt pavement. The dry weight of the three permeable asphalt mixtures with different cycles is shown in Figure 10.  
It can be seen from Figure 10a that the dry weight of the three mixtures increased overall as the number of cycles increased. After 20 spring clogging cycles, the dry weights of OGFC, SBS-OGFC, and COF-OGFC mixtures increased by 7.86%, 9.59%, and 7.33%, respectively. The increase of the mass is due to the fact that the proportion of clogging materials remaining inside the permeable asphalt pavement is gradually increasing. The mass increase rate of SBS-OGFC was always higher than that of the other two asphalt mixtures during the physical clogging procedure. This is because the SBS-OGFC has a larger porosity and can accommodate more clogging materials. Moreover, due to the relatively excellent bonding properties between aggregates in SBS-OGFC, the phenomenon of quality degradation caused by aggregates falling off due to the dynamic water scouring does not occur easily. The dry mass of the OGFC decreased after 12 spring clogging cycles, which may be caused by the spalling of some aggregates on the surface of the specimen under the action of dynamic water scouring. The dry mass of the SBS-OGFC and COF-OGFC decreased after 16 spring clogging cycles, which also indicates that SBS-OGFC and COF-OGFC have better raveling resistance than OGFC. It can be seen from Figure 10b that the dry weight of the three asphalt mixtures increases steadily with the increase of summer clogging cycles in the first 40 cycles, and then the dry weight began to stabilize, which is consistent with the permeability coefficient and porosity results. This also indicated that the clogging materials in the asphalt pavement reached saturation after 40 summer clogging cycles. The mass increase rate of SBS-OGFC is higher than that of COF-OGFC after 50 cycles, indicating that the larger the porosity, the more clogging materials can be accommodated. The mass change of the three asphalt mixtures during the summer clogging procedure is more stable than that during the spring clogging procedure. This is due to the influence of temperature, which was considered in the spring clogging procedure. The adhesive and adhesion properties of the asphalt binder deteriorated  
Figure 10: Dry weight of three permeable asphalt mixtures with different cycles. (**a**) Spring clogging procedure; (**b**) Summer clogging procedure. under the F-T cycles, resulting in a decrease in the overall properties of the asphalt mixture, which easily triggers the loosening of the asphalt mixture under hydrodynamic scouring. Moreover, the coefficient of variation (CV) of the above data was calculated, and the formula for CV is as follows.