WIRING THE WORLD BELOW
Spread across 5 lakh sq-ft, the multi-level Howrah Metro station is 30m below ground level.
The Howrah Station witnesses footfalls of over 10.5 lakh per day. You can imagine the bustle! More than 730 trains ply through two railway yards when the area also has a bus terminus and ferry services across the Hooghly river. With the modern Metro Rail coming up in Kolkata, Howrah will also get a Metro station, which will be one of the deepest Metro stations in the country. At 30m below surface level, once ready, the multi-level Howrah Metro station will cover an area of over 5 lakh sq-ft. Afcons Infrastructure is constructing the diaphragm wall for the station, which at 1.5m, is the thickest to have ever been built in India. The depth of the D-wall is 46m, which is the deepest so far. The depth of excavation for the station is 33m. The station has been designed in a way that it can be connected to the rail yards through a subway and also a foot-over bridge.
The station will have four underground levels – Upper concourse, mechanical and lower concourse and platform. The mechanical level and a part of the concourse levels will be occupied by complex station services, including electrical system, environmental control system (ECS), tunnel ventilation, plumbing and drainage, fire-fighting and signalling. There are four entry and exit points. They consist of three staircases, two lifts and 12 escalators. All the entry and exit points will be integrated under one canopy, resulting in a huge plaza-like structure to provide a grand look.
RISING FROM BELOW THE GROUND
Afcons deployed a state-of-the-art grab machine, BAUER GB -34, from Germany which has large capacity for achieving desired depth. Casagrande B-300 equipped with RKG-14 Kit is being used, which has improved capacity and controls compared to other versions of Casagrande machines. As much as 72 tonnes of reinforcement steel was required for a 6m D-Wall panel. Two split cages weighing 36MT each have been used and the cages have been lifted in one go, using three synchronised cranes of 250MT, 150MT and 60MT capacity. Cage lifting like this is also rare, especially at active railway platforms. Extensive safety measures were taken during lifting of the giant cages. Elaborate traffic management system was put in place to manage passengers and other traffic movement.
Monitoring systems have been installed around the station and adjoining structures to track the impact of construction work on them. Afcons engineers designed Softeye using Styrofoam, which was done for the first time in India, to ensure that the TBMs could cut through the D-walls smoothly. Also, special stripping stop-ends imported from Germany was used for the first time in India. India’s first underwater Metro twin tunnels constructed by Afcons have been selected by the International Tunnelling Association as a poster presentation at the World Tunnel Congress.
The 2.9-km twin tunnels for East-West Metro Project is one of Afcons’ ground-breaking projects