CMRL’s Tunnel Boring Machines Halted for Maintenance Near Thirumayilai

Tunnelling work on the 1.9-km underground stretch between Light House and Thirumayilai under Chennai Metro’s Phase II has been temporarily paused. The two tunnel boring machines (TBMs), Flamingo and Eagle, are undergoing critical cutter head intervention, according to officials from Chennai Metro Rail Limited (CMRL).

Launched nearly two years ago, the TBMs began their journey from Light House station and are now nearing completion of their twin tunnel alignment. The route, part of Corridor 4 connecting Light House to Poonamallee via Thirumayilai and T-Nagar, traverses a densely built area, passing beneath around 160 buildings—including a heritage church, school, and embassy.

“Cutter head intervention is essential due to the heavy wear and tear the TBMs endure,” said a CMRL official. “We’re replacing the cutter tools to ensure safe and efficient boring for the final leg.”

The stretch has posed significant geological challenges. Initial sections had sandy soil near Marina Beach, followed by layers of clay, rock, and abrasive sand, forcing CMRL to replace cutter head parts 25 times so far.

The tunnelling covers three underground stations: Light House, Kutchery Road, and Thirumayilai. Notably, Kutchery Road station is designed as a stacked facility, with Eagle operating in the upper tunnel and Flamingo below. Due to this arrangement, Eagle must be removed first to allow station construction to proceed.

Eagle is set to zoom ahead of Flamingo, which is the latest by the first week of October, though it started first in September 2023. Now, Flamingo is just about 100 metres from Thirumayilai station, and Eagle is around 550 metres from that point.

The intervention and subsequent progress are very important for the completion of time limits and for keeping the momentum going on the ₹61,843 crore Phase II project-the extension of the metro network in the city to up to 118.9 kilometers.