Delhi Metro set to zip past New York Metro in network by December

Minister of Housing and Urban Affairs Manohar Lal Khattar on Thursday said that by December, the network of Delhi Metro would become the largest for a single city, surpassing New York Metro's 399-km record.

“With the opening of the 12-km stretch from Aerocity to Tughlakabad, Golden line, Delhi Metro's network will become the largest single-city network in the world,” said Khattar at a tunnel breakthrough event for Golden Line, held at the Vasant Kunj metro station.

At present, the Delhi Metro's operation network is 394-km-long, he said.

The Minister of Housing and Urban Affairs said Metro networks are operational or projects are in the pipeline across 29 states of the country and the network length today is around 1,000 km, which is the third largest in the world.

“Very soon, we will become a country with the second-largest Metro network, behind China,” he said.

On February 25, Delhi Metro achieved a major construction milestone in Phase 4 with the completion of an underground tunnel between Chhatarpur Mandir and IGNOU Station on the Tughlakabad-Aerocity corridor.

The breakthrough of the Tunnel Boring Machine (TBM) at the IGNOU Station site of the Delhi Metro took place in the presence of Anand Mohan Bajaj, Deputy Comptroller & Auditor General, Commercial, Pramod Kumar, Additional Deputy Comptroller and Auditor General, Vikas Kumar, MD, DMRC, and other senior officials.

A Tunnel Boring Machine (TBM) broke through at IGNOU station after boring an 1475.00 metre-long tunnel. This tunnel breakthrough was achieved using a mammoth 97-metre-long TBM.

Two parallel circular tunnels for up and down movement are being constructed on this stretch as part of the Aerocity–Tughlakabad corridor.

This new tunnel has been constructed at an average depth of approximately 26.0 metre making it one of Delhi Metro's deepest tunnels. The tunnel on the Magenta Line at Hauz Khas has been built at a depth of about 30 metre. About 1,048 rings have been installed in the tunnel, with an inner diameter of 5.8 metre.

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-mechanised casting yard set up at Mundka. The concrete segments were cured with a steam curing system to achieve early strength.

The tunnelling drive for this tunnel started on December 4, 2023 and 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.

As part of the Phase 4 work approved so far, 40.109 km of underground lines are being constructed. The Aerocity-Tughlakabad corridor has underground sections totalling 19.343 km.

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 revolutionised 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 was kicked off in 1998. The first operational section opened on December 25, 2002, connecting Shahdara to Tis Hazari. The entire Phase 1 was operational by 2006 and Delhi Metro's Phase 2 construction began in 2006, Phase 3 in 2011, and Phase 4 in 2019.

In Phase 3, when approximately 50 km of underground sections were built, about 30 TBMs were deployed in the national capital.