The construction of Delhi Metro's Golden Line achieved a major milestone on Thursday as the Tunnel Boring Machine (TBM) broke through at the Vasant Kunj Metro station site after completing a 1.55-km tunneling stretch from Kishangarh.
This underground corridor, which will connect Aerocity to Tughlakabad, is part of the 19.34-km underground stretch of the Golden Line - the fourth phase of the Metro network. The breakthrough of the TBM at the Vasant Kunj Station site of the Delhi Metro took place in the presence of Union Housing and Urban Affairs Minister Manohar Lal Khattar, and Union Minister of State for Housing and Urban Affairs Tokhan Sahu.
Two parallel circular tunnels for up and down movement are being constructed on this stretch as part of the Aerocity-Tughlakabad corridor.
The TBM used for this stretch measures 91 metres in length and was excavated at an average depth of 23 metres, with a minimum depth of 15.7 meters and a maximum of 30.2 metres. The tunnel has an inner diameter of 5.8 meters, and about 1,107 tunnel rings have been installed so far. Another parallel tunnel is also under construction on the same stretch and is expected to be completed by June 2025.
The tunnel has been built using the proven technology of Earth Pressure Balancing Method (EPBM) 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 October 30, 2023 and challenges of steep gradient along with varied geology comprising of mica and hard rock were encountered.
All necessary safety precautions were taken during the construction of the tunnel below the existing 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 kilometres of underground lines are being constructed. The Aerocity-Tughlakabad corridor has underground sections totalling 19.343 kilometres. 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," the Delhi Metro said in a press release. TBMs are particularly useful for underground tunnelling work in congested urban areas. DMRC has been using TBMs for its tunneling work since Phase 1.