Some 19 TBMs are currently engaged in constructing tunnels of Phase 3 of Delhi Metro, where 74 separate tunneling drives are planned. Around 41 km of tunneling and 33 tunneling drives have been completed so far. A total of 35 TBMs have been used during Phase 3, and tunneling is expected to be finished by the end of the year. Commissioning will add 37 km of underground line to the existing 47 km system.
Before commencing each tunneling drive, detailed soil quality, building condition surveys, and corrective measures are undertaken.
The tunneling drives of DMRC have passed without disruption below railway tracks (at Palam, ITO), flyovers (at Munirka, Hauz Khas, Palam), Metro viaducts (at Kalkaji, Janakpuri West, Lajpat Nagar), and Metro tunnels (at IGI Airport).
The use of so many TBMs has enabled construction work through many congested areas such as Old Delhi, Ring Road and Outer Ring Road without any major diversion of the roads or demolition of buildings.