## 5 Analysis and Results
### Construction Time with Tunnel Support Types
For the standard construction time, which includes the usual tunnel supports such as shotcrete and rock bolts, etc., in addition to the basic construction time, the time gradually increases from 74 weeks to 259 weeks with higher support types, and more time is needed for Type 2 than Type 1, unlike the basic construction time. The ratio of the standard operation time increases from 10% to 31% with higher tunnel support types (Figure 4a), which is attributed to the increase in the kinds and amount of tunnel supports, as indicated in Table 2. In addition, the standard advance rate, which is generally used as the usual advance rate of a D&B tunnel, decreases from 40.8 m/week to 11.6 m/week with the variation of support types from Type 1 to Type 5 (Figure 4b), corresponding to 6.8 m/day for Type 1 and 1.9 m/day for Type 5 because there are assumed to be six working days per week (Table 3) in this study. This means that 1.9 and 1.6 blasting rounds can be performed during one day for Types 1 and 5, respectively. For Type 3, in which the round length is 2 m, however, the standard advance rate is 25.6 m/week, i.e., 4.3 m/day, which corresponds to more than two blasting rounds per day. In connection with this, [PERSON] et al. [21] investigated the blasting cycle time (the time spent for one blasting round including the usual tunnel supports) for three Korean tunnels and the results showed that the typical cycle time for Type 3 was approximately 8 h. Hence, it is thought that the advance rate determined in this study is within a reasonable range. The gross construction time covers the operation time for final scaling, water protection and concrete lining in addition to standard construction time, and the gross operation time accounts for between 30% and 14%, decreasing with increasing tunnel support types since little variation occurs in the gross operation time (Table 6), 50 weeks for all the types, but the total construction time increases. The tunnel construction time consists of pavement and various installations in the tunnel, in addition to the gross construction time. It is found that the tunnel operation time excluding the gross construction time is approximately 20 weeks, almost the same for all the tunnel support types, taking between 12% and 5% of total construction time. Lastly, the total construction time covering all the operations, site preparations, and unforeseen rock conditions, etc. (at least 7% of the standard construction time is recommended in the NTNU model), is between 167 and 365 weeks, which corresponds to between 3.8 and 8.2 years, provided that one year is 44 weeks. This means that total construction time of a tunnel of very poor rock mass quality is more than twice that of a tunnel of very good rock mass quality for the same tunnel length. Meanwhile, Table 6 shows a breakdown of the basic, standard and gross operation times. For Type 1, it is found that the operation in which the most time is taken is drilling (144 min), due to the very hard rock mass quality, followed by loading and hauling (129 min) because of the longest round length of Type 1. The rig time is the time needed to move the drilling jumbo to the face, and connect and disconnect the power supply and water, etc. The incidental lost time for drilling and blasting covers the technically dependent lost time occurring at random during tunnelling operations, e.g., machine breakdown, which is assumed to be 10% of the total operation time in the NTNU model [23]. The correction factor for tunnel length and job training is used to consider the variation in operation time resulting from the efficiency in operations according to excavated tunnel length, which is 1 for 3 km tunnel length, i.e., no additional time, as can be seen in Figure 5.  
Regarding the tunnel support operations, shotcrete is generally placed all at once for small thickness, on the other hand, twice or three times in small thickness in the case of large thickness.