Chennai Metro Achieves Major Milestone: Longest Twin Tunnel Completed Between Panagal Park and Kodambakkam

Chennai Metro Rail Limited (CMRL) has achieved a remarkable milestone in its Phase-II expansion with the completion of the city’s longest twin tunnel stretch, running 2.08 kilometres between Panagal Park and Kodambakkam ramp. The final breakthrough was achieved by tunnel boring machine (TBM) ‘Pelican’ on October 15, 2025, marking a significant moment for Chennai’s expanding metro network.

This achievement follows the earlier breakthrough by TBM ‘Peacock’ on July 23, 2025, which completed the parallel tunnel for the same stretch. Together, these two breakthroughs mark the full completion of both up and down tunnels under Corridor-4, Package UG-2 of the Phase-II project.

The tunnelling work, which commenced on March 1, 2024, took 594 days to complete. At a depth of 31.4 metres, engineers and workers successfully navigated through a challenging urban landscape that included fractured rock strata, densely populated neighbourhoods, and critical infrastructure such as Indian Railways tracks and two operational flyovers.

The alignment of the tunnel presented one of the most complex engineering challenges of the project, featuring a tight S-curve with a 206-metre radius and the steepest gradient of +2.581 percent. Despite these difficulties, the project team maintained high safety standards and ensured minimal disruption to the city’s surface activities throughout the construction period.

CMRL’s commitment to sustainability was also highlighted, with its Nandanam headquarters recently receiving the IGBC Platinum certification for adopting green and energy-efficient practices. This recognition underscores the organisation’s continued efforts to promote sustainable infrastructure and reduce the carbon footprint of large-scale urban projects.

The completion of this twin tunnel marks an important step toward improving connectivity under Phase-II, which aims to extend metro access to more areas of Chennai and reduce road congestion. Once operational, this corridor is expected to significantly enhance commuting convenience and contribute to the city’s long-term mobility goals.