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For the first time in Chennai Metro's Phase II project, an underground stretch will be built from Panagal Park to Boat Club through Nandanam, passing under the existing Phase I Nandanam station, and will be done without disturbing the regular metro operations. The Nandanam area will have two metro stations,
one from Phase I (Corridor 1: Wimco Nagar to Airport) and another from Phase II (Corridor 4: Poonamallee to Light House). The new tunnel in Phase II will cross under the old one at Nandanam, forming a perpendicular connection.
Tunnelling Work Done
The tunnelling work, covering 1.9 km, is expected to begin in the first week of December. The Chennai Metro Rail Limited (CMRL) has received approval from the Commissioner of Railway Safety to commence work, as it involves tunnelling under an active metro station. Officials said the existing tunnel lies 16.5 metres deep, while the new one will be at 29.8 metres, leaving a 6.8-metre gap between the two. A tunnel boring machine (TBM) is being lowered at Panagal Park and will begin operation in about three weeks. To ensure safety, CMRL will use Robotic Total Stations, precise instruments that continuously monitor the tunnel area and provide real-time data on any movements or changes. Similar monitoring methods were used earlier under the Kodambakkam railway station.
As the TBM moves from Panagal Park to Nandanam, it will gradually go deeper from 17.3 metres to 29.8 metres. The soil along this route is mostly clayey, though near Nandanam, the machine may face claystone layers due to deeper digging. Officials believe there will be no need to slow down metro trains as they already travel slowly when entering Nandanam station.
