## 3 Results and Analysis
### Migration Law of Wetting Front  
#### 3.2.1 Influence Law of Cement Content on Wetting Front  
The wetting front, as a uniformly wetted infiltration layer and completely non-infiltrated soil layer to separate the interface, can reflect the characteristics of the soil wetting body. The experiment will be a rapid increase in the soil moisture sensor moment recorded as the time of arrival of the wetting front. Different cement contents of the wetting front in the slope body in the direction of two positions to advance the distance and time relationship are shown in Figure 9. From the figure, with the increase in infiltration time, the slope wetting front's rate of advancing distance becomes slower, and due to the formation of slope runoff and under the action of gravity, the advancing rate of the wetting front on the slope and in the slope is different, i.e., in the slope > on the slope. At any point in the whole observation time, the wetting advance distance of the slope decreases with increasing cement content. Figure 8: Variation in runoff and cumulative runoff under different substrate thicknesses. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Thickness of Substrate [cm]** & 0 & 1 & 3 & 5 \\ \hline
**Time of generation of slope runoff [min]** & 13.6 & 10.6 & 9.7 & 8.5 \\ \hline
**Cumulative slope runoff [L]** & 448.76 & 561.59 & 605.43 & 650.26 \\ \hline
**Average slope runoff [mL-min\({}^{-1}\)]** & 1870 & 2340 & 2523 & 2709 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Parameter values without substrate thickness. The relationship between the migration rate of wetting fronts with different cement contents and time is shown in Figure 10, from which it can be seen that the migration rate of wetting fronts decreases rapidly from 0 to 150 min for each slope, the trend of decreasing migration rate of wetting fronts slows down from 150 min to 240 min and the migration rate of wetting fronts tends to be stable after 240 min. To further investigate the correspondence between the wetting front transport rate and time, the power function \(V=a\cdot t^{b}\) pair is fitted (\(a\), \(b\) are constants), where \(V\) is the wetting front transport rate and \(t\) is time. The results of fitting the wet front transport rate versus time for different cement content slopes are shown in Table 6.  
The fitted coefficient of determination \(R^{2}\) is greater than 0.9721, which indicates that the transport rate of wetting fronts at different locations of slopes with different cement contents has a good power function relationship with time and shows the law that the parameter a decreases and the parameter b increases when the cement content increases, \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multicolumn{6}{c}{\(V=a\cdot t^{b}\)} \\ \cline{2-7}  & \multicolumn{3}{c}{**Top of the Slope**} & \multicolumn{3}{c}{**Middle of the Slope**} \\ \cline{3-7}  & & \(a\) & \(b\) & \(R^{2}\) & \(a\) & \(b\) & \(R^{2}\) \\ \hline \multirow{2}{*}{Cement} & 0 & 3.3737 & \(-\)0.4060 & 0.9998 & 3.014 & \(-\)0.3620 & 0.9847 \\  & 1 & 2.8316 & \(-\)0.3849 & 0.9969 & 2.7032 & \(-\)0.3566 & 0.9861 \\  & 3 & 1.2881 & \(-\)0.2557 & 0.9801 & 2.2392 & \(-\)0.3299 & 0.9761 \\  & 5 & 0.9105 & \(-\)0.2283 & 0.9933 & 1.7352 & \(-\)0.3091 & 0.9721 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Fitted table of wetting front transport rate \(V\) versus time \(t\). Figure 10: Transport rate versus time for wetting fronts with different cement contents. Figure 9: The relationship between the distance and time of advancing the wetting front with different cement content. and the linear function \(y=m\cdot x+n\) is used to fit the parameters \(a\), \(b\) (\(m\), \(n\) are constants), \(y\) is the power function parameters \(a\) and \(b\) and \(x\) is the cement content.