## 3 Result and Analysis
### Comparison with Previous Methods  
In order to compare the advantages of the TBM selection decision-making model proposed in this paper with the previous methods, [PERSON]'s TBM selection method is selected as a comparison in this section. According to [PERSON]'s method, the disaster occurrence probability rating (see Table 20) for three projects, the disaster consequence rating (see Table 21) for three different TBMs and the final TBM risk index (see Tables 22-24) are provided. Selection results: In Project 1, the risk rating of open TBM is 56 and that of single-shield and double-shield is 50. Shield TBM should be selected. In Project 2, the open TBM risk rating is 77 and the single-shield and double-shield TBM risk ratings are 55. Shield TBM should be selected. In Project 3, the open TBM risk rating is 83 and the single-shield and double-shield TBM risk ratings are 59. Shield TBM should be selected. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Hazards**} & \multicolumn{3}{c}{**Rating of Likelihood of Hazard Occurrence**} \\ \cline{2-4}  & **Project 1** & **Project 2** & **Project 3** \\ \hline Hard and abrasive rock & 4 & 2 & 3 \\ High water inrush & 2 & 3 & 3 \\ Tunnel wall instability & 2 & 4 & 4 \\ Tunnel face instability & 2 & 4 & 4 \\ Karstic voids & 2 & 3 & 3 \\ Fault zones & 2 & 2 & 3 \\ Squeezing & 4 & 2 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 20: Rating of likelihood of hazard occurrence. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Hazards**} & \multicolumn{3}{c}{**TBM Risk Score of Project 2**} \\ \cline{2-4}  & **Open TBM** & **Double Shield TBM** & **Single Shield TBM** \\ \hline Hard and abrasive rock & 4 & 4 & 4 \\ High water inrush & 12 & 6 & 6 \\ Tunnel wall instability & 20 & 12 & 12 \\ Tunnel wall instability & 16 & 12 & 12 \\ Karstic voids & 15 & 9 & 9 \\ Fault zones & 8 & 4 & 4 \\ Squeezing & 2 & 8 & 8 \\ Total & 77 & 55 & 55 \\ \hline \hline \end{tabular}
\end{table} 
Table 24: TBM risk score of Project 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Hazards**} & \multicolumn{3}{c}{**TBM Risk Score of Project 3**} \\ \cline{2-4}  & **Open TBM** & **Double Shield TBM** & **Single Shield TBM** \\ \hline Hard and abrasive rock & 2 & 2 & 2 \\ High water inrush & 4 & 2 & 2 \\ Tunnel wall instability & 5 & 3 & 3 \\ Tunnel face instability & 4 & 3 & 3 \\ Karstic voids & 5 & 3 & 3 \\ Fault zones & 4 & 2 & 2 \\ Squeezing & 1 & 4 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 21: Rating of consequences of hazard occurrence. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Hazards**} & \multicolumn{3}{c}{**TBM Risk Score of Project 1**} \\ \cline{2-4}  & **Open TBM** & **Double Shield TBM** & **Single Shield TBM** \\ \hline Hard and abrasive rock & 8 & 8 & 8 \\ High water inrush & 8 & 4 & 4 \\ Tunnel wall instability & 10 & 6 & 6 \\ Tunnel face instability & 8 & 6 & 6 \\ Karstic voids & 10 & 6 & 6 \\ Fault zones & 8 & 4 & 4 \\ Squeezing & 4 & 16 & 16 \\ Total & 56 & 50 & 50 \\ \hline \hline \end{tabular}
\end{table} 
Table 22: TBM risk score of Project 1. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Geotechnical Hazards**} & \multicolumn{3}{c}{**TBM Risk Score of Project 2**} \\ \cline{2-4}  & **Open TBM** & **Double Shield TBM** & **Single Shield TBM** \\ \hline Hard and abrasive rock & 4 & 4 & 4 \\ High water inrush & 12 & 6 & 6 \\ Tunnel wall instability & 20 & 12 & 12 \\ Tunnel face instability & 16 & 12 & 12 \\ Karstic voids & 15 & 9 & 9 \\ Fault zones & 8 & 4 & 4 \\ Squeezing & 2 & 8 & 8 \\ Total & 77 & 55 & 55 \\ \hline \hline \end{tabular}
\end{table} 
Table 23: TBM risk score of Project 2.  
higher than that of shield TBM. If the integrity of the rock mass and the radius of the tunnel curve are considered, the results of TBM selection will be more accurate.