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Chennai Metro Rail has reached an important milestone in its Phase 2 expansion. Engineers have completed a difficult tunnelling breakthrough in Kolathur, and at the same time, they launched another tunnel boring machine (TBM) from the very same underground station. This is the first time such an achievement has been
made by any metro system in India.
Challenges Faced During Tunnelling
On Saturday, TBM Mullai successfully broke through at the north shaft of Kolathur station. It had travelled 246 metres from the Kolathur ramp since May 23. The tunnelling team faced several challenges during this task. They had to work with a very shallow overburden of just 1.8 metres above the tunnel, handle a steep gradient of 3.8 per cent, and carefully protect the ground throughout the process. All this work was done under one of the busiest traffic routes in North Chennai. Despite these difficulties, Chennai Metro Rail Limited (CMRL) confirmed that the tunnelling was completed smoothly without affecting traffic or disturbing nearby residents.
At the same time, CMRL launched TBM Kurinji from the station's south shaft. This machine will tunnel 1.06 kilometres toward Srinivasa Nagar. Its route passes through tough Grade-4 and Grade-5 rock and includes a sharp 230-metre curve, making it one of the most challenging parts of Corridor 5.
Achievement For the Operation Team
This simultaneous breakthrough by one TBM and the launch of another is considered a rare engineering feat. It shows the high level of planning and coordination involved in the Chennai Metro Phase 2 project. Corridor 5 is 47 kilometres long, including a 5.8-kilometre underground section where four TBMs, Kurinji, Mullai, Marutham, and Neithal, are being used. Senior officials from CMRL, Tata Projects, and the project's general consultants were present during the operations to monitor progress.
