17 May,2026 04:54 PM IST | Mumbai | mid-day online correspondent
The tunnel includes a 7-kilometre undersea section beneath Thane Creek, which will become India’s first undersea rail tunnel. Pic/Special Arrangement
A major milestone was achieved in the Mumbai-Ahmedabad Bullet Train project after the first cutterhead of a Tunnel Boring Machine (TBM) was lowered at Vikhroli in Mumbai, officials said on Sunday.
An official statement said that the giant cutterhead, which weighs around 350 tonnes and has a diameter of 13.6 metres, marks the final stage in the primary assembly of the TBM's main shield. The machine will be used for the construction of the underground section of the high-speed rail corridor.
Officials said two massive TBMs, each weighing more than 3,000 tonnes, are currently being assembled for the project. These machines will construct a 16-kilometre stretch of the 21-kilometre-long Mumbai tunnel.
The tunnel includes a 7-kilometre undersea section beneath Thane Creek, which will become India's first undersea rail tunnel.
The TBMs being used for the project are the largest ever deployed for railway tunnel construction in the country.
The 13.6-metre-wide cutterhead is designed to excavate a single tunnel capable of accommodating both the up and down railway lines of the bullet train corridor.
According to officials, the cutterhead weighs nearly the same as around 250 midsize passenger SUVs. It arrived at the site in five separate shipments and was assembled using around 1,600 kilograms of high-precision welding.
The unit is fitted with 84 cutter discs, 124 scrapers and 16 bucket lips.
These components help in cutting rock, clearing debris and removing excavated material from the tunnel, officials said.
The TBM will travel nearly six kilometres from Vikhroli towards Bandra-Kurla Complex (BKC), passing beneath dense urban areas and the Mithi River, an official said.
The machine will eventually be retrieved at the under-construction Mumbai Bullet Train station at BKC, officials said.
Officials said several advanced monitoring systems are being used to ensure safe tunnelling operations and protect nearby structures during excavation.
The systems include Surface Settlement Points (SSP), Optical Displacement Sensors (ODS), 3D Reflect Targets and Strain Gauges.
These instruments will help engineers closely monitor movement, pressure and vibrations during tunnel construction.
