The Delhi Metro Rail Corporation (DMRC) has completed the tunnelling work on its deepest underground stretch of Phase 4, achieving a significant milestone with a tunnel boring machine (TBM) breakthrough at the IGNOU station site. This newly constructed tunnel connects Chhatarpur Mandir to IGNOU on the Aerocity-Tughlakabad corridor (Golden Line).
The tunnel, which runs at an average depth of 27 meters (ranging from 15 to 39 meters), is one of Delhi Metro’s deepest. The completion of a parallel tunnel on February 25, 2025, marked the conclusion of tunnelling for both the up and down lines on this challenging stretch.
To construct the tunnel, DMRC used the Earth Pressure Balancing Method (EPBM), installing around 1,048 precast concrete rings with an internal diameter of 5.8 meters, DMRC said in an official release.
Overcoming significant challenges, including varied geological conditions with steep slopes, mica and hard rock, the TBM’s screw auger was damaged and had to be replaced during the operation, DMRC said. CM Rekha Gupta and Environment Minister Manjinder Singh Sirsa attended the event.
The Aerocity-Tughlakabad corridor includes 19.3 kilometers of underground sections as part of the 40.1-kilometer Phase 4 expansion. The rapid progress is evident, with DMRC achieving three TBM breakthroughs in the last month alone. TBMs have played a crucial role in the metro’s expansion, minimising surface disruption.