The first breakthrough in the 21-kilometre tunnel between Bandra-Kurla Complex (BKC) in Mumbai and Shilphata in Thane, part of the Mumbai-Ahmedabad high-speed rail corridor, was achieved on Wednesday, according to the National High Speed Rail Corporation Limited (NHSRCL).

A continuous 2.7 km section was completed using the New Austrian Tunnelling Method (NATM). The tunnel includes a 7-km undersea stretch beneath Thane Creek, forming a critical element of India’s Rs 1.08 trillionl bullet train project—approximately USD 13 billion.

Of the total 21 km, 16 km will be constructed with Tunnel Boring Machines (TBMs) and 5 km using NATM, especially between Shilphata and Ghansoli. To expedite work, an Additionally Driven Intermediate Tunnel (ADIT) was built, enabling excavation from both ends. Around 1.62 km has been excavated from Shilphata, and overall NATM progress stands at 4.3 km.

The NHSRCL stated that safety measures such as ground settlement markers, piezometers, inclinometers, strain gauges, and biometric access systems have been installed to ensure secure tunnelling without affecting nearby structures or the environment.

Although the shafts and launch systems are ready, Tunnel Boring Machines are yet to arrive for the 16-km section.