The National High-Speed Rail Corporation Ltd (NHSRCL) has initiated the construction of a 21-kilometer tunnel between Bandra Kurla Complex (BKC), Mumbai, and Shilphata, Thane, marking India’s first undersea rail tunnel. This tunnel, a part of the Mumbai-Ahmedabad bullet train project, will span 7 kilometers under the sea and utilize advanced methods such as the Tunnel Boring Machine (TBM) and New Austrian Tunneling Method (NATM). The remaining 5 kilometers will be constructed using the NATM.
Undersea Rail Tunnel: The tunnel will be 21 kilometers long, with a 7-kilometer stretch under the sea, connecting BKC and Shilphata, Thane.
Construction Methods: Advanced methods like TBM and NATM will be employed for the tunnel construction. TBMs with a 13.6-meter cutter head diameter will cover approximately 16 kilometers, and the remaining 5 kilometers will be constructed using NATM.
Tunnel Depth: The depth of the tunnel will range from 25 to 57 meters below ground level, with the deepest point being 114 meters beneath the Parsik hill near Shilphata.
Shafts and Portals: Three shafts, located at BKC, Vikhroli, and Sawli, Thane district, and an inclined shaft at Ghansoli will aid in the construction. Portals at Shilphata and ADIT Portal are also part of the project.
– Shaft 1 at Mumbai HSR Station (BKC) has completed 100% of its secant piling work.
– Shaft 2 at Vikhroli is undergoing excavation and will serve as the entry point for two tunnel boring machines.
– Shaft 3 at Sawli (near Ghansoli) is undergoing excavation.
– Portal work has commenced at Shilphata, marking the NATM end of the tunnel.
– ADIT Portal is being constructed to facilitate additional access to the underground/undersea tunnel.
Challenges and Mitigations: Challenges include controlled blasting techniques to minimize noise and air pollution, construction in densely populated areas with existing utilities, and proper disposal of excavated material under regulatory supervision.
Supporting Facilities: Concurrent construction of supporting facilities like gantry cranes, labor colonies, and site offices to facilitate the overall progress of the project.
The Mumbai-Ahmedabad bullet train project aims to enhance high-speed rail connectivity, with this undersea rail tunnel being a significant milestone in its development.