CMRL to Start Tunnelling 2.2-km Thirumayilai to Boat Club Metro Stretch in August

Chennai Metro Rail Limited (CMRL) is set to commence tunnelling for a 2.2-kilometre underground stretch of the Phase II project from Thirumayilai to Boat Club, passing through Alwarpet and Bharathidasan Road, in the first week of August. The work, which is part of Corridor 4, was previously scheduled to begin in June.

Due to limited underground space, CMRL will employ a stacked tunnel design between the Thirumayilai and Bharathidasan Road stations. In this section, one tunnel will be constructed directly above the other, rather than the standard side-by-side configuration used in other locations.

Two tunnel boring machines (TBMs) are currently being lowered and assembled at the Thirumayilai station. Once launched, the machines will drill through Alwarpet and Bharathidasan Road before being retrieved at the Boat Club station. The drilling process will begin with the TBM on the down line, followed by the machine on the up line.

Metro officials expect to encounter hard rock and clayey soil during the initial stretch from Thirumayilai to Bharathidasan Road. CMRL officials noted that drilling continuously through hard rock could slow down early progress and require frequent replacement of the TBM cutter discs, which are the tools that help in excavation.

After passing Bharathidasan Road, the machines are expected to encounter mostly clayey soil, which will allow for easier and faster drilling. Officials estimate that the entire tunnelling process from Thirumayilai to Boat Club will take approximately one and a half years to complete.

The 2.2-kilometre stretch is a key component of the larger 118.9-kilometre Phase II project, which comprises three corridors: Corridor 3 (Madhavaram to SIPCOT), Corridor 4 (Poonamallee to Light House), and Corridor 5 (Madhavaram to Sholinganallur). The upcoming work follows the completion of another underground section from Light House to Thirumayilai.