NEW DELHI: The Delhi Metro Rail Corporation (DMRC) on Tuesday completed tunnelling on the underground section of the Delhi Metro’s Phase 4 expansion project, with a tunnel boring machine achieving breakthrough at the site of the IGNOU station on the Golden Line’s Aerocity-Tughlakabad corridor.
Chief Minister Rekha Gupta and Industries Minister Manjinder Singh Sirsa were present as chief guests during the breakthrough event.
This new tunnel has been constructed at an average depth of approximately 27 metres (minimum depth 15 metres & maximum 39) making it one of Delhi Metro’s deepest tunnels.
It is pertinent to mention that work on another parallel tunnel between Chhatarpur Mandir and IGNOU was completed on 25th February 2025. Therefore, tunnelling work on both the up and down lines has been completed on this challenging stretch.
The tunnel on the Magenta Line at Hauz Khas in Phase 3 was built at a depth of about 30 metres while another tunnel for the Airport Express Line passes below the Rajiv Chowk Metro station at about 45 metres.
About 1048 rings have been installed in this tunnel, with an inner diameter of 5.8 metres. The tunnel has been built using the proven technology of EPBM (Earth Pressure Balancing Method) with a concrete lining made of precast tunnel rings. These tunnel rings were cast at a fully mechanized casting yard set up at Mundka. The concrete segments were cured with a steam curing system to achieve early strength.
This tunnelling drive faced challenges of steep gradient along with varied geology comprising mica and hard rock were encountered due to which the screw auger got damaged and was replaced during the drive. All necessary safety precautions were taken during the construction of the tunnel below the existing viaduct and built-up structures. Ground movements were monitored with highly sensitive instruments fixed on nearby structures, ensuring that there was no settlement anywhere.
The TBM broke through this morning at IGNOU Station after boring a 1460.00 meter-long tunnel. This tunnel breakthrough was achieved using a mammoth 97-metre-long TBM. It is significant to mention that DMRC has achieved three TBM breakthroughs in the last four weeks signifying the rapid progress being made in Phase 4 underground work.
As part of the Phase 4 work approved so far, 40.109 kilometres of underground lines are being constructed. The Aerocity-Tughlakabad corridor has underground sections totaling 19.343 kilometres.