Transport tunnels under Hooghly set a record

KOLKATA, Jun 24: On June 20, the Kolkata Metro Rail Corporation (KMRC) completed the construction of India’s first set of underwater transportation tunnels. The two tunnels, 16.1 metres apart, with a diameter of 5.5 metres each, link the two banks of the Hooghly river — Howrah Maidan and Sealdah on one side with Kolkata on the other. The tunnels are at a depth of 13 metres below the riverbed, and 30 metres from the land surface.
On April 14, a day considered auspicious in many parts of the country, a German-made Earth Pressure Balancing Tunnel Boring Machine named Rachna touched the riverbed — and it reached the other end on May 23. The same day, the second tunnel boring machine named Prerna started tunnelling the riverbed and came out on the other side on June 20.
“This is the first underwater transportation tunnel passing through a mighty river. The tunnels are an engineering marvel, which we have been able to complete in just 66 days,” Satish Kumar, Managing Director, KMRC, told The Hindu.
With the completion of the tunnels, India has joined a select group of nations that have underwater transport, he said, adding that the feat comes almost 33 years after the first metro train in the country opened its doors for the public in Kolkata in 1984.
Mr. Kumar explained that the two tunnel-boring machines could not work parallel to each other because of the soft clay soil under the riverbed. After one machine completed the tunnelling, the second TBM followed. (Agencies)