## 3 Quantitative Analysis of Landslide Deformation Area  
### Quantitative Analysis Methods  
Quantitative analysis of a landslide deformation region mainly refers to calculating the area and volume of the landslide during the period from the beginning to the end of instability, calculating the average rate of change of the landslide area and volume within 5 min time according to the obtained area and the volume of the landslide at each moment, and drawing the quantitative analysis curves of deformation area, which are the cumulative area percentage curve, cumulative volume percentage curve, area change rate curve, and volume change rate curve, respectively. The data used in this study are mainly images and point clouds containing depth information, which were accumulated from the model experiments completed by the subject group in recent years. The acquisition was conducted by a trinocular stereo camera that recorded the side slope every 3 s after the experiment started and then transmitted it to the computer for saving. These data investigate various factors affecting the stability of rainfall slopes, including the intrinsic configuration of the slope and external factors. The area and volume of slope damage were obtained by the software compiled by our group. The landslide identification software is shown in Figure 2. The main steps of the software operation are 2-8. Firstly, the angle of the slope, the image and point cloud at the moment of T\({}_{0}\), and the image and point cloud at the moment of T\({}_{n}\) are input in order. Then, select the appropriate threshold value. Finally, click the calculation button to obtain the area and volume of slope damage at the moment of T\({}_{n}\). To facilitate the comparison of experiments with different model sizes, the specific landslide area and landslide volume, as well as the rate of change of area and volume, were obtained and converted into percentage form. The area share and volume share of the landslide damage area are obtained by dividing the landslide area and volume by the total area of the slope surface and the total volume of the side slope, respectively. The principle of calculating the area and volume of the landslide is shown below. Landslide area calculation: As shown in Figure 3a, the landslide image recorded by the trinocular camera is processed and recognized, the number of pixels contained in the fault area is identified, and the number of pixels in the landslide failure area is determined according to the actual area of the known slope and the total pixels contained in the slope to determine the percentage of the number of pixels in the landslide failure area to the total number of landslide pixels, and then the area of the landslide is calculated. The calculation formula is as follows (1):  
\[S=S_{0}\frac{n}{N} \tag{1}\]  
where S is the landslide area, \(S_{0}\) is the slope area, \(n\) is the number of pixels contained in the fault area, and N is the total number of pixels contained on the slope surface. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\
\begin{tabular}{c} **Working** \\ **Condition** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Experimental** \\ **Grouping** \\ \end{tabular} } & \multicolumn{6}{c}{**Experimental Variables**} \\ \cline{3-8}  & & **Rainfall** & **Slope** & **Slope** & **Compaction** & **With or Without** & **Vegetation** \\  & & **Intensity** & **Angle** & **Crest** & **of Subsoil** & **Perimeter Pressure** & **Cover Density** \\ \hline \multirow{6}{*}{4} & S11 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & Low Density & / \\  & S12 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & General & / \\  & S13 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & High Density & / \\  & S14 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & / & 0 m/s \\  & S15 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & / & 5.6-5.8 m/s \\  & S16 & 60 mm/h & 30\({}^{\circ}\) & None & / & / & / & 7.3-7.6 m/s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cont.