NEW DELHI: The Delhi Metro Rail Corporation (DMRC) reached a significant milestone today by completing the tunnelling work on the deepest underground stretch of Phase 4. This achievement was celebrated with the breakthrough of a tunnel boring machine at the IGNOU station site on the Aerocity – Tughlakabad corridor, also known as the Golden Line.
The event was attended by the Chief Minister of Delhi, Smt. Rekha Gupta, and Delhi’s Minister of Industries, Food & Supplies, and Environment, Forest & Wild Life, Sh. Manjinder Singh Sirsa.
The newly constructed tunnel reaches an average depth of approximately 27.0 meters, with a minimum depth of 15.0 meters and a maximum of 39 meters, making it one of the deepest tunnels in the Delhi Metro network. It is noteworthy that the construction of another parallel tunnel between Chhatarpur Mandir and IGNOU was completed on February 25, 2025. Consequently, tunnelling work on both the up and down lines has been successfully completed on this challenging stretch.
For comparison, the tunnel on the Magenta Line at Hauz Khas in Phase 3 was built at a depth of about 30 meters, while the tunnel for the Airport Express Line passes below the Rajiv Chowk Metro station at approximately 45 meters.
DMRC MARKS HISTORIC TUNNEL BREAKTHROUGH AT IGNOU STATION; COMPLETES TUNNELLING WORK ON PHASE 4’S DEEPEST STRETCH
— Delhi Metro Rail Corporation (@OfficialDMRC) March 18, 2025
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… pic.twitter.com/08IVcdkFmX
A total of 1048 rings have been installed in this tunnel, each with an inner diameter of 5.8 meters. The tunnel was constructed using the EPBM (Earth Pressure Balancing Method) technology, with a concrete lining made of precast tunnel rings. These tunnel rings were produced at a fully mechanized casting yard established at Mundka and cured using a steam curing system to achieve early strength.
The tunnelling drive faced numerous challenges such as steep gradients and varying geology, including mica and hard rock. These conditions resulted in damage to the screw auger, necessitating its replacement during the drive. Despite these obstacles, all necessary safety precautions were meticulously followed during the construction of the tunnel beneath the existing viaduct and built-up structures. Ground movements were continuously monitored using highly sensitive instruments attached to nearby structures to ensure there was no settlement.
This morning marked a significant milestone as the Tunnel Boring Machine (TBM) successfully broke through at IGNOU Station after boring a 1460.00-meter-long tunnel. The breakthrough was accomplished using a massive 97-meter-long TBM. It is noteworthy that the Delhi Metro Rail Corporation (DMRC) has achieved three TBM breakthroughs in the last four weeks, showcasing the rapid progress being made in Phase 4 underground construction.
| 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 Phase 4, a total of 40.109 kilometers of underground lines are currently being constructed, with the Aerocity-Tughlakabad corridor accounting for 19.343 kilometers of underground sections.
Tunnel Boring Machines (TBMs) are sophisticated machines specifically designed to excavate tunnels with a circular cross-section through various soil and rock strata. These machines are capable of boring through hard rock, sand, and other materials, making them indispensable for tunnel construction projects worldwide. TBMs have transformed the tunneling industry by enabling the construction of tunnels without disrupting surface structures such as buildings.
TBMs are particularly beneficial for tunneling projects in densely populated urban areas where space is limited. The Delhi Metro Rail Corporation (DMRC) has been utilizing TBMs for tunneling work since Phase 1 of its construction. In Phase 3, which involved constructing approximately 50 kilometers of underground sections, around 30 TBMs were deployed in the national capital.
