India is poised to make a significant leap in global engineering with the development of its first underwater bullet train tunnel, stretching 21 kilometres beneath the Arabian Sea. This ambitious venture is part of the broader Mumbai-Ahmedabad High-Speed Rail Corridor, which aims to transform travel between two of the nation’s most crucial cities.
The construction will deploy advanced Tunnel Boring Machines (TBMs) to carve out a path from Bandra-Kurla Complex (BKC) in Mumbai to Shilphata, passing through the Thane Creek’s intertidal zone. This segment will traverse depths ranging from 25 to 65 metres, presenting substantial engineering challenges due to complex geological formations and sensitive marine environments.
In contrast to metro systems, which typically use TBMs with cutter heads around 5-6 metres in diameter, this project will utilise larger TBMs with diameters of 13.1 metres. To excavate the 16-kilometre tunnel segment, three TBMs will be employed, while the remaining 5 kilometres will be completed using the New Austrian Tunnelling Method (NATM). This significant infrastructure will support bullet trains reaching speeds of up to 320 kilometres per hour. The tunnel will feature two tracks for bidirectional travel within a single tube, with construction concentrated at key points including Ghansoli, Shilphata, and Vikhroli. Excavation is slated to commence in Ghansoli, where the initial TBM will begin its journey towards Thane Creek from a depth of 39 metres.
India’s experience with underwater tunnels is not new; it includes a tunnel under the Hooghly River for the Kolkata Metro and another beneath the Mithi River for Mumbai’s Line 3. The decision to build this tunnel underwater was driven by the need to protect the ecologically sensitive Flamingo Sanctuary and Mangrove Forest in Thane Creek, as well as to circumvent the complexities of land acquisition in Mumbai’s densely populated areas. The National High-Speed Rail Corporation Limited (NHSRCL) has committed to stringent environmental protocols during excavation, employing controlled blasting techniques to mitigate noise and air pollution, ensuring the project’s alignment with environmental standards while advancing infrastructure development.
