India's first Mumbai-Ahmedabad bullet train to give travellers undersea experience, but building it no easy feat

The undersea tunnel can be built only during high tides, limiting the working period to just 4-5 hours.

MUMBAI: Nearly seven kilometres of upcoming high-speed bullet train project connecting two major metropolis – Mumbai and Ahmedabad – will lie under the sea. For the first time in India, travellers will experience this spectacular feat of riding under the sea near Thane creek at a maximum speed of 350 km per hour.  

But building this undersea stretch in no easy feat.

“About 7 km of the 21 km long tunnel will be undersea. We need to know the strata which are good enough for the tunnel to cross through,” said Achal Khare, Managing Director of National High-Speed Rail Corporation Limited. 

Nearly 66 boreholes, about 250 metres apart from each other, are being dug near the Thane creek. Special equipment and technology have been borrowed from the Japanese. 

“We have dug 66 boreholes about 250 metres apart from each other. To know the strata between these boreholes, we have got equipment from a Japanese Company, which is doing the work for us,” said Khare. 

The boreholes were dug after geotechnical and geophysical investigation were undertaken for the entire project.

“The work here can be done only during high tides because the ground is very slushy. So working period is limited to only 4-5 hours. It is tough to control the boat along the Central Line which takes people to and fro, so Japanese have trained one of us to control it,” added Khare.

The work for under the sea tunnel is expected to be completed by August 15, 2022.

“We're aiming to complete project by 15th August 2022, which is the mandate given to us. The underwater tunnel will be started next year and will be completed by the end of 2022,” said Khare.

The cost of the tunnel is estimated at Rs 3,500 crores. The cost of the total train project is Rs 1.10 trillion, and Japan is giving a loan of Rs. 88,000 crores for the same at a minimal interest of 0.1 per cent, which has to be repaid over 50 years. 

“It is a very generous term,” added Khare.

In September 2017, Prime Minister Narendra Modi and his Japanese counterpart Shinzo Abe laid the foundation stone of the ambitious bullet train project.