New Delhi: The Delhi Metro Rail Corporation (DMRC) achieved a major construction milestone in phase 4 (Golden Line) with the completion of an underground tunnel between Chhatarpur Mandir and IGNOU Station on the Tughlakabad – Aerocity corridor on Tuesday.
The breakthrough of the tunnel boring machine (TBM) at the IGNOU station site of the Delhi Metro took place in the presence of deputy comptroller & auditor general, commercial, Anand Mohan Bajaj, additional deputy comptroller & auditor general Pramod Kumar, managing director of DMRC Vikas Kumar and other senior officials.
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A TBM broke through this morning at IGNOU station after boring an 1475.00 meter-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. The breakthrough on the other parallel tunnel is planned to be achieved in the month of March 2025.
This new tunnel has been constructed at an average depth of approximately 26.0 meters (min depth 15.0 mtr & max. 36) 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 metres. About 1048 rings have been installed in the tunnel, with an inner diameter of 5.8 meters.
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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 mechanized 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 4th December, 2023 and challenges of steep gradient along with varied geology comprising of mica and hard rock were encountered due to which the screw auger got damaged and was replaced during the drive.
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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 kilometres of underground lines are being constructed. The Aerocity-Tughlakabad corridor has underground sections totalling 19.343 kilometres.
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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 revolutionized 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. In Phase 3, when approximately 50 kilometres of underground sections were built, about 30 TBMs were deployed in the national capital.
