The first underwater tunnel in India is being built as part of the East-West Metro Corridor’s project, and it will take about 45 seconds for trains to cover the 520-meter stretch. The tunnel that goes under the Hoogly river in West Bengal is being touted as the Indian version of Eurostar’s London-Paris corridor. An estimated cost of Rs 120 crores is being spent on the project.
The tunnel, which is about 2.5 kilometres long, is expected to be commissioned in 2023 following the completion of the section between Sealdah and Esplanade.
The tunnel runs through the Salt Lake Sector V IT hub metro station in the east to Howrah Maidan in the west under the river. The construction of the tunnel has already been completed, and it is expected to be operational in December 2023 following the completion of a 2.5-kilometer section between Sealdah and the Esplanade.
Kolkata Metro Rail Corporation General Manager (Civil) Sailesh Kumar. informed PTI that the underwater alignment was the only choice for the project’s planners as it was the only option that avoided challenges like uprooting residential areas or other technical issues.
The project, which was approved in 2009, has been marred by various delays and cost escalations. As per officials, the cost of the project has nearly doubled in the last 13 years. Out of the estimated budget of Rs 8,475 crore Rs 8,383 crore has already been spent.
The tunnel’s internal diameter is 5.55 meters and its external diameter is 6.1 meters. The spacing between its up and down tunnels will be around 16.2 meters.
The tunnel’s inner walls are being made using high-quality concrete segments that are reinforced 275mm thick. Six of these segments are being used to create a circular lining around the circumference of the tunnel. These are being pre-cast using special moulds imported from Korea.
In order to prevent water from the Hoogly river from entering the tunnel, various measures have been taken. These include the use of special concrete mixes that are composed of micro silica and fly ash. The inner walls of the tunnel are being sealed using a process known as grouting. This process involves filling the space between the concrete segments with grout.
These components are being used to prevent water from entering the tunnel through the jointed sections. The inner walls of the tunnel have also been equipped with special auxiliary gaskets that are made of hydrophilic and neoprene.
The emergency evacuation shafts inside the tunnel are being made to accommodate up to 760 meters long. These are being provided to ensure the safety of passengers. These shafts are being installed in the Howrah Station and the Strand Road station.
The underground corridor of the East-West Metro is approximately 10.8 kilometres long. It passes through the Phoolbagan and Howrah station areas. The rest of the route is elevated.