## 2 Acquisition of the Original Database
### Designation of Representative Measurement Points  
Figure 2a depicts the establishment of a three-dimensional finite element model of the tunnel in the karst areas, with the axial length of the tunnel model as X, the circumferential length of the tunnel model as Y, and the height of the tunnel model as H. In the numerical model established, the axial length of the tunnel is taken as 90 m and the vertical distance between the karst cave and the tunnel entrance is taken as 30 m. The upper boundary of the three-dimensional model of the numerical simulation of karst tunnel construction is the free surface. The three-dimensional displacement constraint should be imposed \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Influencing factors** & Elastic modulus & Poisson’s ratio & Geotechnical weight & Cohesion & Internal friction angle & Tunnel diameter \\ \hline
**Label symbol** & A1 & A2 & A3 & A4 & A5 & A6 \\ \hline
**Influencing factors** & The diameter of the karst cave & Clear distance between the tunnel and karst cave & Location of the karst cave & Tunnel depth & Excavation dimension \\ \hline
**Label symbol** & A7 & A8 & A9 & A10 & A11 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Correspondence between influencing factors and code names. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
**Levels** & **A1** & **A2** & **A3** & **A4** & **A5** & **A6** & **A7** & **A8** & **A9** & **A10** & **A11** & \(\begin{array}{c}d\\ /mm\end{array}\) & \begin{tabular}{c} **S1** \\ /MPa** \\ \end{tabular} & \begin{tabular}{c} **S1** \\ /MPa** \\ \end{tabular} & \begin{tabular}{c} **S1** \\ /MPa** \\ \end{tabular} & \
\begin{tabular}{c} **S1** \\ /MPa** \\ \end{tabular} &
\begin{tabular}{c} **S1-S3** \\ /MPa** \\ \end{tabular} \\ \hline  
& 1 & 86.950 & 3.185 & 1.273 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Influencing factors and their levels. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Case** & **A1** & **A2** & **A3** & **A4** & **A5** & **A6** & **A7** & **A8** & **A9** & **A10** & **A11** \\ \hline
1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 17.264 & 0.532 & 0.342 \\
2 & 1 & 1 & 1 & 1 & 2 & 2 on the side boundary of the numerical simulation model of karst tunnel. The bottom boundary of the numerical simulation model of the karst tunnel should be subjected to the displacement constraints in three directions. The numerical simulation model of the karst tunnel could be established by ABAQUS general finite-element software, which is an engineering simulation software developed by Dassault Systemes in France. The three-dimensional numerical simulation models of the karst tunnel were built by ABAQUS 2019 version of finite element software. In the process of karst tunnel excavation, whether the surrounding rock of the tunnel reaches the plastic state could be taken as the standard to determine the stability of the surrounding rock of the karst tunnel. The three levels of karst cave size are 1 m, 3 m, and 5 m, as shown in Figure 2b. For the selection of the most representative and general measuring points for tunnel construction in karst areas, the 1 st working condition, the 10 th working condition, and the 19 th working condition in the orthogonal test design table are selected for the representative analysis of the measuring points. As shown in Figure 3a-c, the vertical displacement at the tunnel entrance and at the vault and the arch bottom at 30 m from the tunnel entrance are more significant than in other parts of the tunnel under Case 1, Case 10, and Case 19. When taking the vertical displacement as a target variable, the measurement points could be chosen from the vault and the arch bottom at the tunnel entrance and the vault and the arch bottom at a distance of 30 m from the tunnel entrance. According to the Mohr-Coulomb strength theory, the angle between the normal to the breaking surface and the first principal stress of a rock and soil mass is \(45^{\circ}+\varphi/2\).