CMRL to construct underground passage under operational Phase I tunnel in Nandanam

CHENNAI: In one-of-a-kind initiative, the Chennai Metro Rail is planning to construct an underground passage from Panagal Park to Boat Club as part of its Phase II project, where the route would pass directly beneath the operational Phase I tunnel at Nandanam station.

According to a report in The Hindu, the 1.9-kilometre stretch will give the Nandanam area a unique feature that has two metro stations, which would serve different corridors. There would be one route from the initial phase and another one from the new line, and officials said that the construction would take place in such a way that it would not disrupt the train services.

The project is expected to hit the road by next month, as the necessary approval from the Commissioner of Railway Safety has been obtained. The new tunnel will be built at a depth of 29.8 metres and will pass perpendicularly under the existing Phase I tunnel, which has been constructed at a depth of 16.5 metres. Officials said that a buffer of 6.8 metres will separate the two structures.

Authorities said that a tunnel boring machine is already being set up at Panagal Park and is scheduled to begin work by December. They further added that while the terrain between Panagal Park and Boat Club is primarily clay, the machine is expected to encounter disintegrated clay stone in the deeper strata near Nandanam station.

Officials noted that there would be no need to reduce the speed of the train in train during the tunnelling process as trains will mandatorily slow down while entering the station.