DMRC MARKS HISTORIC TUNNEL BREAKTHROUGH AT IGNOU STATION; COMPLETES TUNNELLING WORK ON PHASE 4’S DEEPEST STRETCH
The Delhi Metro Rail Corporation (DMRC) today completed tunnelling work on the deepest underground stretch of Phase 4 with the breakthrough of a tunnel boring machine at the IGNOU station site (from Chhatarpur Mandir) on the Aerocity – Tughlakabad corridor (Golden Line).
This unique feat was achieved in the august presence of the hon’ble Chief Minister of Delhi, Smt. Rekha Gupta. Delhi’s Minister of Industries, Food & Supplies and Environment, Forest & Wild Life, Sh. Manjinder Singh Sirsa was also present on the occasion.
This new tunnel has been constructed at an average depth of approximately 27.0 meters (min depth 15.0 mtr & max. 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, now tunnelling work on both the up and down lines have 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 meters. 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 of 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.
| Recent TBM Breakthroughs | |||
| Date | Location of TBM Breakthrough | Phase 4 Corridor | Length |
| 25.02.2025 | IGNOU | Aerocity – Tughlakabad | 1,475 mtrs |
| 06.03.2025 | Vasant Kunj | Aerocity – Tughlakabad | 1,550 mtrs |
| 18.03.2025 | IGNOU | Aerocity – Tughlakabad | 1,460 mtrs |
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 totalling 19.343 kilometres.
A TBM is a machine used to excavate tunnels with a circular cross-section through various soil and rock strata. They can be designed to bore through anything from hard rock to sand. TBMs have revolutionized tunnelling work worldwide, enabling tunnels to be bored without disturbing buildings and other surface structures.
TBMs are particularly useful for underground tunnelling work in congested urban areas. DMRC has been using TBMs for its tunnelling work since Phase 1. In Phase 3, when approximately 50 kilometres of underground sections were built, about 30 TBMs were deployed in the national capital.
