# Suitability Evaluation of the Lining Form Based on Combination Weighting-Set Pair Analysis
## 4 Case Study
### Suitability Evaluation  
According to Equation (22) and combined with Tables 2 and 5, the suitability evaluation of seven groups of drilling samples for the reinforced concrete lining is carried out. The five-element connection degree of working points is shown in Table 6, and the results of each evaluation method are shown in Table 7. According to the evaluation results, all the high-pressure pipelines of the PSPS are basically suitable for reinforced concrete linings. From No. 1 to No. 7, with the increasing underground depth, the anisotropy of the high-pressure pipeline section gradually increases and the suitability of the reinforced concrete lining form gradually decreases, which is mainly due to the influence of in situ stress and surrounding rock classification.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Index** & **Expert 1** & **Expert 2** & **Expert 3** & **Expert 4** & **Expert 5** & **Expert 6** & **Expert 7** & **Expert 8** \\ \hline \(A\) & 3 & 2.5 & 2 & 1 & 1.5 & 1 & 1.5 & 1.2 \\ \(B\) & 1 & 2 & 1.5 & 2 & 1.5 & 2 & 1 & 1.5 \\ \(C\) & 2 & 2.5 & 2.5 & 2.5 & 2.5 & 3 & 2.5 & 3 \\ \(D\) & 2.5 & 2.5 & 2 & 2.5 & 1.5 & 2 & 2.5 & 1.5 \\ \(E\) & 1.5 & 1 & 2 & 2 & 3 & 2.5 & 2.5 & 3 \\ \hline \end{tabular}
\end{table}
Table 4: Index importance scores.  
\begin{table}
\begin{tabular}{c c c c} \hline
**No.** & **Professional Field** & **Position** & **Educational Level** \\ \hline Expert 1 & Geological Engineering & Senior Engineer & Master \\ Expert 2 & Geological Engineering & Senior Engineer & Master \\ Expert 3 & Geological Engineering & Professor & Doctor \\ Expert 4 & Geological Engineering & Professor & Doctor \\ Expert 5 & Hydraulic Engineering & Senior Engineer & Master \\ Expert 6 & Hydraulic Engineering & Senior Engineer & Master \\ Expert 7 & Hydraulic Engineering & Professor & Doctor \\ Expert 8 & Hydraulic Engineering & Professor & Doctor \\ \hline \end{tabular}
\end{table}
Table 3: Expert Information.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Suitability** & **Extremely** & **More** & **Basically** & **Relatively** & **Extremely** \\
**Level** & **Suitable (I)** & **Suitable (II)** & **Suitable (III)** & **Unsuitable (IV)** & **Unsuitable (V)** \\ \hline \(\mu\) & [0.6, 1] & [0.2, 0.6) & [\(-\)0.2, 0.2) & [\(-\)0.6, \(-\)0.2) & [\(-\)1, \(-\)0.6) \\ \hline \end{tabular}
\end{table}
Table 5: The Relationship between the Five-element Connection Degree and the Suitability Level.  
By comparison, the results of the three methods are basically the same, except that the results of the three evaluation methods for No. 7 are slightly different (Table 7). The expert evaluation method shows that the rating level of the site is relatively unsuitable. The reason for this is that the experts believe that the surrounding rock classification has declined and the hydraulic gradient value is too large, which makes the use of reinforced concrete lining more unfavorable. However, the involved experts might have different knowledge backgrounds and insights, and consequently the determination of the weight coefficient varies from person to person. The evaluation level calculated by the objective combination weighting-SPA method is more suitable. Objective weight combination weighting is based on the measured data, using certain mathematical methods to objectively assign the weight of the evaluation index. The method lacks subjective control and is often prone to be inconsistent with the actual situation. In summary, for the evaluation process of the suitability of reinforced concrete lining form, using only one of the methods is not comprehensive enough, which might result in over- or under-estimation of the results. Therefore, the combination weighting method integrates the advantages of the subjective and objective weighting methods, combines expert knowledge while fully considering the objectivity of the sample data, minimizes the loss of information, and improves the evaluation reliability.