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Chennai Metro Rail Limited (CMRL) is getting ready to start tunnelling in November on one of the toughest parts of its Phase II project, the stretch between Thiruvanmiyur and Indira Nagar, according to sources. Two tunnel boring machines (TBMs) will be used to dig twin tunnels covering about 650 metres between these two stations.
Metro Corridor to Connect Routes
This work is part of Corridor 3, a 45.8 km line that will run from Madhavaram to SIPCOT through Adyar. Of this, 26.8 km will be underground. When finished, the corridor will connect commuters across nearly 40 important locations, including Indira Nagar and Thiruvanmiyur. Officials stated that excavation work at the Thiruvanmiyur station site has been going on for a few weeks. One TBM has been lowered into the site, and the second machine is expected to be placed soon.
Difficulties Leading to Delays
However, the team is facing serious difficulties because of the hard underground rock. Digging has currently reached a depth of 22 metres. The area has dense granite, which will likely slow down the work. Usually, digging such a short section would be quick due to the difficult conditions, but building both tunnels may take up to a year. An official explained that if the TBM drills through hard rock continuously, the discs on the cutter head will wear out fast. When that happens, workers need to perform a cutterhead intervention, a process where parts are replaced. This may have to be done several times for both machines on this stretch, which will further delay the work.
Overall, while the tunnelling is set to begin soon, the challenging geology means that progress will be slower than usual, and the work may take much longer to complete.
