## 4 Results and Discussion
### Statistical Results of Clogging Materials
#### 4.1.2 Particle Size of Clogging Materials  
A sieving analysis test was carried out for the collected clogging materials, and the test results are summarized in Tables 9 and 10. It can be seen from Tables 9 and 10 that the particle size distribution of the clogging materials in spring and summer seasons shows a large difference. In the summer season, the proportion of coarse sand and very coarse sand is small, the proportion of medium sand, fine sand, very fine sand, and silt is large, and more than 90% of clogging materials has a particle size below 600 \(\upmu\)m. However, the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Granularity** & **Size** & **No. 1** & **No. 2** & **No. 3** & **No. 4** & **No. 5** & **No. 6** & **No. 7** & **No. 8** \\ \hline Very coarse & 1180–2360 & 2.73\% & 5.12\% & 1.3\% & 3.62\% & 2.69\% & 0\% & 2.06\% & 0.93\% \\ sand & \(\upmu\)m & 4.34\% & 10.7\% & 2.11\% & 6.94\% & 2.62\% & 1.53\% & 5.42\% & 1.78\% \\ Medium & 300–600 & 20.17\% & 22.04\% & 28.74\% & 23.11\% & 12.4\% & 19.21\% & 10.27\% & 28.44\% \\ sand & \(\upmu\)m & 150–300 & 30.52\% & 17.3\% & 17.63\% & 28.68\% & 27.31\% & 20.41\% & 22.84\% & 18.1\% \\ Very fine & 75–150 & 23.07\% & 18.39\% & 30.22\% & 16.74\% & 20.44\% & 22.36\% & 28.67\% & 30.63\% \\ sand & \(\upmu\)m & 23.07\% & 18.39\% & 30.22\% & 16.74\% & 20.44\% & 22.36\% & 28.67\% & 30.63\% \\ Salt & \(\sim\)75 \(\upmu\)m & 19.17\% & 26.45\% & 20\% & 20.91\% & 34.54\% & 36.49\% & 30.74\% & 20.12\% \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Particle size distribution of clogging materials at different collection locations in the summer season. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Granularity** & **Size** & **No. 1** & **No. 2** & **No. 3** & **No. 4** & **No. 5** & **No. 6** & **No. 7** & **No. 8** \\ \hline Fine gravel & 2360–4750 & 10.85\% & 12.74\% & 52.4\% & 44.8\% & 8.74\% & 9.32\% & 7.63\% & 6.74\% \\ Very coarse & 1180–2360 & 23.44\% & 19.88\% & 20.74\% & 30.74\% & 12.69\% & 20.77\% & 18.69\% & 27.32\% \\ sand & 600–1180 & 19.53\% & 20.76\% & 12.54\% & 10.1\% & 20.53\% & 18.4\% & 20.74\% & 30.98\% \\ Medium & 300–600 & 25.75\% & 27.43\% & 7.85\% & 8.49\% & 29.87\% & 20.68\% & 14.63\% & 14.48\% \\ Fine sand & 150–300 & 11.6\% & 10.3\% & 2.33\% & 3.33\% & 18.43\% & 29.16\% & 35.55\% & 14.36\% \\ Very fine & 75–150 & 5.79\% & 5.98\% & 3.17\% & 1.74\% & 5.34\% & 1.44\% & 1.03\% & 3.79\% \\ Salt & \(\sim\)75 \(\upmu\)m & 3.04\% & 2.91\% & 0.97\% & 0.8\% & 4.4\% & 0.23\% & 1.73\% & 2.33\% \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Particle size distribution of clogging materials at different collection locations in the spring-thawing season. Figure 6: Clogging materials’ coverage density at different collection locations. proportion of fine sand, medium sand, coarse sand, and very coarse sand in clogging materials in the spring season is large, the proportion of very fine sand and silt is small, and only about 40% of clogging materials have a particle size below 600 \(\upmu\)m. The reason for the existence of clogging materials with a large particle size in the spring-thawing season is that the clogging materials cannot be cleaned daily, and most clogging materials are frozen on the road surface. Secondly, throwing \"anti-slip\" sand on the pavement surface in winter is also an important factor causing the general increase of the particle size of the clogging materials. The particle size of the clogging materials for the concrete pavement is generally smaller than for the asphalt pavement, and the proportion of very fine sand for the clogging materials for the concrete pavement is higher than that for the asphalt pavement, which may be due to the smooth surface of the concrete pavement and the sufficient compaction of the vehicle. The particle size of clogging materials in the non-overloaded case is generally smaller than that of the heavy-duty road. This may be due to the higher cleaning frequency of the non-overloaded road.