New Delhi: The underground tunnel between Maa Anandmayee Marg and Tughlaqabad railway colony station has been completed on the Tughlaqabad-Aerocity corridor of phase IV, also known as Golden Line. A tunnel boring machine (TBM) broke through on Saturday morning at Tughlaqabad railway colony station after boring a 0.79km-long tunnel. This tunnel breakthrough was achieved using a mammoth 96-metre-long TBM. Two parallel circular tunnels for up and down movement are being constructed on this stretch. The breakthrough on the other parallel tunnel is expected to be achieved in July 2025.The tunnel breakthrough occurred in the presence of transport minister Pankaj Kumar Singh and DMRC managing director Vikas Kumar. Singh said, “Going forward, we will further accelerate metro expansion and ensure that Delhi’s citizens receive the quality infrastructure and services they truly deserve.”This new tunnel was constructed at an average depth of around 18 metres. About 566 rings were installed in the tunnel, with an inner diameter of 5.8 metres. The tunnel was built using the proven technology of the 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.“All necessary safety precautions were taken during the construction of the tunnel below the existing built-up structures. Ground movements were monitored with highly sensitive instruments fixed on nearby structures, ensuring that there was no settlement anywhere,” said Anuj Dayal, principal executive director of corporate communications at Delhi Metro Rail Corporation.As part of the phase-IV work approved so far, 40.11km underground lines are being constructed. The Aerocity-Tughlaqabad corridor has underground sections totalling 19.34km.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 I. In phase III, when approximately 50km underground sections were built, about 30 TBMs were deployed in the national capital.
