DMRC achieves major milestone in Phase-4 with tunnel breakthrough on Tughlakabad-Aerocity corridor

New Delhi: The Delhi Metro Rail Corporation (DMRC) has reached a significant construction milestone in Phase 4 with the successful completion of an underground tunnel between Chhatarpur Mandir and IGNOU Station on the Tughlakabad-Aerocity corridor.

A Tunnel Boring Machine (TBM) broke through at the IGNOU Station site after excavating a 1,475-meter-long tunnel. The breakthrough was achieved in the presence of Anand Mohan Bajaj, Deputy Comptroller & Auditor General, Commercial; Pramod Kumar, Additional Deputy Comptroller & Auditor General; Dr Vikas Kumar, MD, DMRC, and other senior officials. A second parallel tunnel for the up and down movement is expected to be completed by March 2025.

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One of Delhi Metro’s Deepest Tunnels

Constructed at an average depth of 26 meters, the tunnel reaches a maximum depth of 36 meters, making it one of Delhi Metro’s deepest underground passages. The tunnel at Hauz Khas on the Magenta Line, by comparison, is built at a depth of 30 meters. The newly constructed tunnel comprises 1,048 rings with an inner diameter of 5.8 meters.

The tunneling was executed using the Earth Pressure Balancing Method (EPBM), with concrete lining made of precast tunnel rings, which were cast at a mechanized facility in Mundka. To enhance durability, the segments underwent steam curing for early strength development.

Overcoming Engineering Challenges

The tunneling drive, which commenced on December 4, 2023, faced geological challenges, including a steep gradient and varied strata comprising mica and hard rock. A damaged screw auger had to be replaced during the process. Despite these hurdles, all necessary safety precautions were maintained, with continuous ground movement monitoring using high-sensitivity instruments to prevent structural settlements.

Expanding Delhi Metro’s Underground Network

Under Phase 4, DMRC is constructing 40.109 kilometers of underground metro lines, with the Aerocity-Tughlakabad corridor accounting for 19.343 kilometers. TBMs have been instrumental in executing tunneling projects in congested urban areas without disturbing surface structures. DMRC has extensively deployed TBMs since Phase 1 and used nearly 30 TBMs in Phase 3 to construct approximately 50 kilometers of underground metro sections.

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