Chennai Metro Rail marks twin tunnel boring milestones

CHENNAI: Chennai Metro Rail Limited (CMRL) has achieved a remarkable milestone in its Phase II expansion with the simultaneous breakthrough of one Tunnel Boring Machine (TBM) and the launch of another at Kolathur station on Corridor 5.

Corridor 5 stretches 47 km, featuring a 5.8-km underground section and 41.2 km of elevated track. Four TBMs — Kurinji, Mullai, Marutham, and Neithal — are being deployed along the underground portion.

CMRL reported that TBM Mullai successfully broke through at the north shaft of Kolathur station. The drive, which began on May 23, covered 246 metres and navigated significant challenges, including a minimal overburden of 1.8 metres, a steep gradient of minus 3.8%, and continuous ground protection in a high-traffic urban area. The breakthrough was completed without impacting public movement or traffic.

At the same time, TBM Kurinji was launched from the south shaft of Kolathur station to start tunnelling towards Srinivasa Nagar station. This 1,060-metre stretch passes through Grade-5 and Grade-4 rocky strata and includes a sharp 230-metre curve.

CMRL highlighted that this marks the first time in India that one TBM has been launched while another has achieved a breakthrough within the same underground metro station — a milestone showcasing advanced engineering and project execution.