Metro tunnel boring machine to Boat Club to pass under Nandanam station

For the first time in the Phase II network, Chennai Metro Rail will build an underground network from Panagal Park to Boat Club, via Nandanam, under the existing Nandanam station in Phase I network without affecting train operations.

The Nandanam locality in the city will have two stations, one for the Phase I network (falling under Corridor I from Wimco Nagar to Chennai Airport via Nandanam) and one for the Phase II network (as part of Corridor 4 from Poonamallee to Light House via Nandanam).

The Phase II tunnel linking Panagal Park-Nandanam-Boat Club will be built in a way that it will perpendicularly cross underneath the Phase I tunnel at Nandanam.

In the first week of December, Chennai Metro Rail is likely to commence the work to build a tunnel from Panagal Park to Boat Club via Nandanam, spanning a distance of 1.9 km

Chennai Metro Rail has now received the crucial approval from the Commissioner of Railway Safety, which is mandatory since tunneling is going to be carried out under a functional Nandanam station and the existing tunnel.

According to officials of Chennai Metro Rail Limited (CMRL), at Nandanam, the depth of the existing tunnel is nearly 16.5 meters, and the Phase II tunnel will come up at nearly 29.8 meters (nearly 98 feet) from the ground. Between the floors of the Phase I tunnel to the top of the tunnel structure or its crown, there will be a gap of 6.8 meters

The first tunnel boring machine (TBM) is currently being lowered at the Panagal Park station readying for the launch in three weeks.

“To ensure the safety of the Nandanam station and tunnel, we will continuously monitor the influential zone using an instrument called ‘Robotic Total Stations,’ a surveying high precision instrument deployed for constant monitoring of the tunnel, providing real-time data about the structure, settlements and other deformations. Just as we carried out tunneling under the railway track at Kodambakkam railway station, here too, we will keep track to maintain safety,” an official said.

At Panagal Park, when the TBM starts its journey, it will bore at a depth of 17.3 meters below the ground, but by the time the machine reaches Nandanam, the depth will be 29.8 meters.

Sources said that between Panagal Park and Boat Club, the machine is expected to encounter mostly clayey soil. “But at Nandanam station, the machine may hit some disintegrated clay stone, as here TBMs will go to the deeper strata [since there is operational metro on Anna Salai],” a source said.

It is still not clear if the speed of the train will be decreased when the TBM bore under the Nandanam station. Officials said, since the train will anyway enter the station at a lesser speed, they don’t foresee the need to reduce the speed.