India completed first undersea tunnel for Mumbai–Ahmedabad bullet train

India’s Mumbai–Ahmedabad Bullet Train project marks a major milestone with the completion of its first undersea tunnel section beneath Thane Creek, paving the way for the country’s high-speed rail ambitions.

The completion of the first stretch of India’s first undersea rail tunnel marks a crucial milestone in the Mumbai-Ahmedabad Bullet Train project. A 2.7-kilometre section of the projected 21-kilometre tunnel connecting Bandra-Kurla Complex (BKC) and Shilphata has been successfully excavated, marking the first breakthrough beneath Thane Creek. This section of the tunnel was built using modern Tunnel Boring Machines (TBMs) and the New Austrian Tunnelling Method (NATM). To expedite the NATM segment, a parallel shaft was constructed, allowing excavation to proceed from both ends simultaneously.

This undersea tunnel is part of a bigger high-speed rail system capable of supporting trains travelling at speeds of up to 320 kilometres per hour. With the tunnel breakthrough complete, emphasis turns to other essential civil works along the corridor. Notably, nearly 300 kilometres of viaducts have been finished, and 16 of the planned 21 bridges, including the newly completed Daman Ganga River bridge in Valsad, are now operational. However, the project has encountered a logistical challenge: three TBMs required for the remaining tunnel work are currently delayed at a Chinese port, potentially impeding progress. Indian authorities are seeking diplomatic solutions to speed their release.

Meanwhile, construction of stations, electrical infrastructure, and tracks is progressing steadily, particularly in Gujarat and Maharashtra. Trial runs are expected to commence in Gujarat in 2026, with the project completed by 2028. This underwater tunnel breakthrough marks a significant engineering achievement in India’s effort to construct its first bullet train track.