The Delhi Metro Rail Corporation (DMRC), a joint venture between the Government of India and Delhi, has reached a key milestone in Phase 4 Golden Line with the completion of an underground tunnel between Chhatarpur Mandir and IGNOU Station on the Tughlakabad-Aerocity corridor.
The tunnel boring machine (TBM) breakthrough occurred at the IGNOU Station site of the Delhi Metro.
TBM successfully broke through at IGNOU Station after boring a 1,475m-long tunnel.
According to DMRC, the breakthrough was made using a massive 97m-long TBM.
Two parallel circular tunnels for up and down movement are being built for the Aerocity-Tughlakabad corridor.
The breakthrough for the second tunnel is scheduled for next month.
Delhi Metro said the new tunnel, constructed at an average depth of 26m, is one of Delhi Metro’s deepest.
The Magenta Line tunnel at Hauz Khas was built at a depth of about 30m.
A total of 1,048 rings, with an inner diameter of 5.8m, were installed. Built using the EPBM (Earth Pressure Balancing Method), the tunnel features precast concrete rings. These rings were cast at a fully mechanised yard in Mundka and steam-cured to achieve early strength.
The tunnelling for this project began on 4 December 2023, facing challenges such as a steep gradient and varying geology, including mica and hard rock.
DMRC implemented strict safety measures during tunnel construction beneath existing viaducts and structures. Ground movements were monitored using sensitive instruments on nearby buildings, ensuring no settlement anywhere.
As part of the Phase, 40.1km of underground lines are being constructed, with the Aerocity-Tughlakabad corridor comprising 19.3km of underground sections.
A TBM is used to excavate tunnels with a circular cross-section through various soil and rock types. Designed to bore through everything from hard rock to sand, TBMs have advanced tunnelling by allowing excavation without disrupting surface structures.
It also helps in underground work in densely populated urban areas. DMRC has utilised TBMs since Phase 1, and in Phase 3, around 30 TBMs were deployed for the construction of 50km of underground sections in Delhi.
In December 2024, Delhi Metro announced the completion of the tunnelling drive for Phase 4.
TBM Amrit, operated by Afcons Infrastructure, finished the tunnel boring between the Tughlakabad Airforce launch shaft and Maa Anandmayee Marg Station on the Tughlakabad-Aerocity corridor.
