New Delhi, July 14 -- India's bullet train project achieved a major milestone Monday when the first section of the 21-kilometre undersea tunnel between BKC (Bandra-Kurla Complex) and Thane made a breakthrough.

The 2.7-km tunnel section, part of the Mumbai-Ahmedabad bullet train project, has been constructed between Ghansoli and Shilphata in Maharashtra.

Out of the total 21 km, 5 km is being constructed using the New Austrian Tunnelling Method (NATM) between Shilphata and Ghansoli, while the remaining will be built using Tunnel Boring Machines (TBMs). The tunnel also includes a 7-km-long undersea section beneath Thane Creek, the ministry of railways said in a statement.

To expedite tunnelling in the NATM portion, an Additionally Driven ...