# Stability Prediction of Soil Slopes Based on Digital Twinning and Deep Learning
## 4 Results  
### Optimization of Non-Circular Slip Surface  
The non-circular slip surfaces consisted of line segments connected by multiple control points. The safety factors were different for different numbers of control points. Based on 30 original slopes, the safety factors and optimization times of circular slip surfaces and non-circular slip surfaces with different numbers of control points are compared in this section. The comparison results are shown in Tables 6 and 7. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{\ \begin{tabular}{c} **Slope** \\ **Num.** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Circular** \\ **Slip** \\ **Surface** \\ \end{tabular}  } & \multicolumn{6}{c}{**Safety Factors of Non-Circular Slip Surface with Different Number**} \\ \cline{3-10}  & & & & & & **of Control Points** & & \\ \cline{3-10}  & & **  
In comparison, it was found that for most slopes, the safety factor of a non-circular slip surface gradually decreases with the increase of the number of control points, and for very few slopes, the safety factor of a non-circular slip surface fluctuates with the increase of the number of control points. The change in the safety factor with each increase in the number of control points does not exceed 0.1. When the control points of the non-circular slip surface of the 12 th slope were 6 and 7, the maximum difference in the safety factor was 0.0816. The difference between the maximum value and the minimum value of the safety factor of the noncircular slip surface was 0.1047 and 0.1052 for the 12 th and 30 th slopes, respectively, and the difference for other slopes was not larger than 0.1, but the optimization time greatly increases with the increase of the control points. Since the six control points can roughly reflect the shape of the slip surface of the soil slope, in this paper, the non-circular slip surface with six control points was used to calculate the safety factor of the three-thousand generated slope samples. By comparing the minimum safety factor of the non-circular sliding surface with that of the circular sliding surface, it was found that the safety factor of the non-circular sliding surface is smaller than that of the circular sliding surface, as shown in Figure 17. Among them, the difference in the safety factor of the 2 nd, 12 th, 18 th, 20 th, 24 th, and 30 th slopes is 0.202, 0.155, 0.161, 0.160, 0.100, and 0.118, respectively, and the difference of the other slopes is not larger than 0.1. The slope stability states were classified according to Table 1. Except for the 9 th and 17 th slopes, the stability states of the slopes determined based on the safety factors of the circular slip surface and the non-circular slip surface were the  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{\ \begin{tabular}{c} **Slope** \\ **Num.** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Circular** \\ **Slip** \\ **Surface** \\ \end{tabular}  } & \multicolumn{6}{c}{**Optimization Time of Non-Circular Slip Surface with Different Numbers**} \\ \cline{3-10}  & & & \multicolumn{6}{c}{**of Control Points**} & \\ \cline{3-10}  & & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** \\ \hline
1 & 17.6 & 32.2  
same, but the calculation time of the safety factors of the non-circular slip surface was 4-50 times that of the circular slip surface. For the 9 th and 17 th slopes, the safety factors of the circular slip surface were 1.1080 and 1.0527, respectively, which were basically stable slopes, but the minimum safety factors of the non-circular slip surface were 1.0217 and 1.0445, respectively, which were metastable slopes.