CMRL's Twin Tunnel Triumph: Longest Stretch Finished

Chennai Metro Rail Limited (CMRL) has reached a major milestone in its Phase-II expansion with the successful completion of the city’s longest twin tunnel stretch between Panagal Park and the Kodambakkam ramp.

The 2.08-km tunnel was completed following the final breakthrough by Tunnel Boring Machine (TBM) Pelican on 15 October 2025. This follows the earlier breakthrough by TBM Peacock on 23 July, marking the completion of both the up and down tunnels under Corridor-4, Package UG-2. The tunnelling commenced on 1 March 2024 and was completed in 594 days, overcoming complex geological and urban challenges.

At a maximum depth of 31.4 metres, the tunnel alignment navigated fractured rock formations, densely built-up areas, Indian Railways tracks, and two active flyovers. It also included a tight S-curve with a 206-metre radius and the steepest gradient in the project at +2.581%, demonstrating advanced engineering execution in a highly constrained urban environment.

In a parallel development, CMRL’s headquarters at Nandanam has received the IGBC Platinum certification, highlighting the agency’s continued commitment to sustainable and green infrastructure.

News by Rahul Yelligetti.