The Delhi Metro Rail Corporation (DMRC) has achieved a major construction milestone with a successful tunnelling breakthrough at Tughlakabad Railway Colony station on the upcoming Golden Line, part of Phase 4 of the metro expansion.

According to a DMRC statement, the tunnel connects Maa Anandmayee Marg to Tughlakabad Railway Colony on the Tughlakabad-Aerocity corridor. The breakthrough was achieved by a Tunnel Boring Machine (TBM) after completing a 792-metre stretch in the presence of Delhi Health and Transport Minister Pankaj Kumar Singh, DMRC Managing Director Dr Vikas Kumar and other senior officials, it said.

The corporation said TBMs are designed to bore through various soil and rock layers, while minimising disruption to the surface. They are especially effective in urban settings and have been used extensively in previous metro phases.

DMRC said the tunnel, located at an average depth of 18 metres, is one of two parallel tunnels being built for up and down movement on the corridor. The breakthrough on the second tunnel is expected by July 2025.

A total of 566 tunnel rings, each with an inner diameter of 5.8 metres, were installed using the Earth Pressure Balancing Method (EPBM), the statement said. The precast concrete segments used in the tunnel lining were manufactured at a mechanised casting yard in Mundka and steam-cured for early strength.

DMRC said the ground movement was carefully monitored during the tunnelling to avoid any surface settlement under existing structures.

Under Phase 4, 40.1 km of underground metro lines are being constructed, with the Tughlakabad-Aerocity corridor accounting for 19.3 km of that stretch, it added.

The latest development marks another step forward in the ongoing expansion of the Delhi Metro network, aiming to enhance connectivity and ease urban transportation challenges in the national capital, it said.