Deepestmetroventilationshaft

The East West corridor metro project is underway in Kolkata, which saw a milestone on Monday, with the completion of the deepest Metro ventilation shaft in India. The base slab of the escape shaft is 43.5 metres below the ground level, equivalent to a 15storey building.

Kolkata got its first-ever underwater twin rail transportation tunnels and the deepest underground metro station from Howrah metro station, which surpassed Hauz Khas and Chawri Bazaar metro stations in Delhi. The project, a joint effort of Afcons and the KMRC, will not only provide ventilation to the tunnels, but will also be used in evacuation operations during emergencies.

The evacuation shaft is located at Strand Road near river Hooghly and is situated between the two tunnels.

At the Howrah Metro Station, where the tunnels start entering the river, the tunnel invert is 30 m deep. From there, the tunnels' depth inreases to 37 metre up to invert level while crossing the riverbed. The Diaphragm Walls had to be constructed 56 metre deep from ground level as per the base demand of the geometric profile of the tunnel alignment. This necessitated the ventilation shaft to go as deep as 43.5 metre.

"The metro shaft has been constructed adopting innovative engineering techniques and methodology to navigate geological challenges and overcome any impact on Kolkata’s circular railway track along river Hooghly," said Satya Narayan Kunwar, the Afcons project manager.

The escape shaft’s base slab is 43.5 m deep, equivalent to a 15-storey building.