The National High Speed Rail Corporation Limited (NHSRCL) has started assembling Tunnel Boring Machines (TBMs) for a 16-km tunnel section of the Mumbai-Ahmedabad bullet train project in Maharashtra. This development marks the progress on one of the most complex parts of India’s first high-speed rail corridor.
The 16-km stretch is part of a larger 21-km tunnel planned between Bandra Kurla Complex (BKC) and Shiphata. This section will also include India’s first 7-km undersea tunnel beneath Thane Creek. As per NHSRCL, 5 km of tunnelling using the New Austrian Tunnelling Method (NATM) has already been completed, whereas the remaining 16 km will be constructed using TBMs.
“The lowering and assembly of the Tunnel Boring Machine (TBM) has begun for the construction of a 16 km long tunnel,” NHRSCL stated.
What makes this tunnel important?
The tunnel will be a single-tube structure of 13.1 meters in diameter designed to carry twin tracks for the bullet train. It will be operated at a depth of about 25 to 57 metres below ground, with the deepest point reaching 114 meters below Parsik hill.
This underground section is seen as one of the most significant engineering components of the Mumbai-Ahmedabad High Speed Rail project.
How is the construction work being carried out?
According to NHSRCL, the process started at Vikhroli, where one of the six segments of the TBM’s main shield, weighing about 170 metric tonnes, was brought down to a depth of 56 metres below ground level. It will be roughly equal to a 20-storey building.
Two TBMs have been brought in for the work. One will move from Vikhroli towards BKC, whereas the other will start from Sawli, near Ghansoli and move towards Vikhroli. To support this development, three shafts have been constructed at BKC, Sawli and Vikhroli.
When will the tunnelling start?
The machines are currently being assembled and will start operations after testing and commissioning.
Initial TBM drive is scheduled for July 2026
The main drive will take place in October 2026.
Each machine is around 95.32 metres long and is over 3,000 tonnes and is designed to work in difficult geopolitical conditions using Mix Shield/slurry technology.
How are tunnel segments being prepared?
A dedicated casting yard at Mahape in Thane district is already producing tunnel lining segments for the 16-km TBM portion. NHRSCL stated that around 77,000 segments will be cast from 7,700 rings. Esch rings will have nine curved segments and one key segment.
The agency also mentioned that several monitoring tools, including settlement sensors and seismographs, are being used to ensure safe excavation and protect nearby structures.