In Delhi’s belly, nine tunnel boring machines dig deep to connect metro corridors

New Delhi: Deep below the city’s crowded roads, historic neighbourhoods and bustling commercial hubs, nine tunnel boring machines (TBMs) are at work across Delhi.

These TBMs are machines used to excavate tunnels with a circular cross-section. The macines can bore into a variety of soil and rock strata. They can be designed to bore through anything from hard rock to sand. This technology has revolutionised the way tunnelling work is done worldwide, as tunnels can now be bored without disturbing the buildings and other structures on the surface.

Delhi Metro Rail Corporation (DMRC) is building over 38 km of underground sections as part of its Phase IV expansion. The TBMs are weaving an intricate network of tunnels that will connect new corridors.

Of the nine machines, four are working on the Golden Line — two between Aerocity and Mahipalpur, one at Aerocity towards the launching shaft and two between Vasant Kunj and Mahipalpur. The remaining five are operating on the Magenta Line, including two each between Ramkrishna Ashram Marg and Nabi Karim and Sadar Bazar and Pulbangash.

“Though nine TBMs are at work on different stretches of the capital, there are 15 TBMs in total in Delhi right now. The other six are at different stages (of tunnel creation),” a DMRC official said.

In Phase IV, DMRC has completed 23 tunnel breakthroughs in different parts of the city. “This is a major engineering achievement as these breakthroughs were achieved on diverse terrain, often below areas with high population concentration,” the official said.

He added that overall around 84% of the civil work is complete on the Phase-IV priority corridors, including Aericity-Tughlakabad on the Golden Line and Krishna Park Extension to Deepali Chowk and Majlis Park to Ramakrishna Ashram Marg on the Magenta Line. The tunnelling work is also under way for the Inderlok-Indraprastha corridor, which is an extension of the Magenta Line.

On the Golden Line, Delhi metro has six TBMs working at the same time in a stretch of 5-6 km to expedite work. “Six TBMs functioned almost in parallel between the Air Force Launching Shaft and Sarita Vihar depot on the Golden Line and successfully completed the tunnelling there. While five TBMs are currently operating between Vasant Kunj and Aerocity, another machine is ready on site to be launched at Kishangarh towards Vasant Kunj on the Golden line itself,” the official added.

DMRC has also floated a tender for the design of four underground stations from Shivaji Stadium to the proposed Kartavya Bhawan station as part of tunnelling work for the upcoming Central Vista corridor. The other two stations are Yuge Yugeen Bharat (near Rakabganj Gurudwara) and Central Secretariat. This is part of the new corridor from RK Ashram Marg to Indraprastha is an extension of the Magenta Line under the Phase V(A) expansion.

The tender has been issued “for design verification, detail engineering, supply, installation, testing and commissioning of electrical and mechanical system, DG sets, environment control system, tunnel ventilation systems and building management system for four underground stations,” a DMRC official said.

In April, DMRC also invited bids of Rs 3.2 crore for a detailed design consultant for construction of the Central Vista depot near Majlis Park. The RK Ashram to Indraprastha corridor will provide connectivity to all the Kartavya Bhawans. Around 60,000 office-goers and 2 lakh visitors will benefit from this corridor.

After this corridor is added, the Magenta Line corridor will become 88.4 km, making it the longest in the networkl. The Magenta Line will l also have 21 interchange stations, which will also be the most in the network.