## 6 Data Analysis of Line 2  
The RAM analysis for Line 1 of the Isfahan metro is presented using two different methods. The results indicate that the Markov method should be performed for the availability analysis, and the reliability and maintainability analysis should be completed according to the probability distribution function of each subsystem. The Pareto diagram was developed to see the frequency of EPBM failures in Line 1, which is presented in Figure 9. This diagram shows that more attention should be given to the mechanical subsystem concerning planning and maintenance for a successful project. Further, based on observations and the maintainability diagram, cutterhead inspection is the central aspect of maintenance time. Although the geological structure of the ground is similar in Lines 1 and 2, the geological maps of Line 2 show an increase in the cemented conglomerate sections at the face of the tunnel compared to Line 1, and the excavation must mainly be performed in  
Figure 8: Maintainability of the EPBM and all subsystems in Line 1. Figure 9: Pareto analysis of EPBM subsystems in Line 1.  
mixed face conditions (i.e., rock and soil). Thus, the decision was made to refurbish the cutterhead of the EPBM before starting excavation for Line 2 by changing the position of the foam system, replacing the grout pump, and redesigning the segment mover at the bridge area. The old and new cutter heads are presented side by side in Figure 10.  
The results obtained by performing the same analysis as Line 1 for Line 2 over the initial seven months of the construction are presented in Figures 11 and 12 and Tables 8-10. An improvement is expected in the Reliability of the system in Line 2 following minor refurbishments, revised preventive maintenance operations (PM), and strict controls on mechanical and electrical parts per shift, day, week, and month. This can be further improved as the personnel gain familiarity with the machine, and more expert supervising engineers are hired. However, due to different ground conditions, it is impossible to forecast the cutterhead TTRs and TBFs in Line 2. The results show that the maintainability of the machine for Line 2 has not changed significantly compared to Line 1, although the MTTR of the mechanical subsystem improved from 1.64 to 0.87 h.  
Tables 8 and 9 show that the MTTR and \(\upmu\) of the electrical and cutterhead are the same in Lines 1 and 2. This indicates that the required time for repairing and changing electrical parts and cutting tools cannot be reduced. In Line 2, changing the cutterhead improved the M(t), but experiencing more challenging geological conditions declined the M(t). Because of this, changes in the M(t) values are negligible between the two lines, as seen in Figure 12. \begin{table}
\begin{tabular}{l l c c} \hline \hline
**Method Line** & **Data Set** & **Electrical** & **Mechanical** & **Cutterhead** \\ \hline \multirow{2}{*}{Line 1} & \(\lambda\) & 0.085 & 0.205 & 0.041 \\  & \(\upmu\) & 1.450 & 0.610 & 0.050 \\ \multirow{2}{*}{Line 2} & \(\lambda\) & 0.027 & 0.080 & 0.024 \\  & \(\upmu\) & 1.379 & 1.144 & 0.045 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Availability of EPBM in Lines 1 and 2. \begin{table}
\begin{tabular}{l l c} \hline \hline
**Availability of System** & **Line 1** & **Line 2** \\ \hline P\({}_{0}\) & EPBM Availability & 0.45 & 0.61 \\ P\({}_{1}\) & Electrical subsystem Unavailability & 0.03 & 0.01 \\ P\({}_{2}\) & Mechanical subsystem Unavailability & 0.15 & 0.04 \\ P\({}_{3}\) & Cutterhead subsystem Unavailability & 0.37 & 0.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Availability of EPBM in Lines 1 and 2. Figure 12: Reliability (**a**,**c**) and Maintainability (**b**,**d**) of EPBM and two subsystems in Lines 1 and 2. According to Table 9, it can also be seen that the mechanical subsystem has the most improvement both in \(\lambda\) and \(\mu\). The reliability value has improved because of PM works. Tables 8 and 9 indicate that MTBF/\(\lambda\) of all subsystems has significantly increased/decreased.