Published Date: 17-05-2026

A significant milestone was achieved for the Mumbai-Ahmedabad Bullet Train project with the lowering of the first cutterhead of Tunnel Boring Machine (TBM) at Vikhroli in Mumbai (Maharashtra). With a diameter of 13.6 meters, weighing a massive 350 tonnes, this component marks the final step in the primary assembly of the TBM’s main shield.

Two TBMs, each weighing over 3,000 tonnes, are currently being assembled to construct a 16 km portion of the 21 km Mumbai tunnel. This includes a 7 km stretch under Thane Creek, which will serve as India’s first undersea rail tunnel. These machines are the largest ever deployed for rail tunnel construction in the country.

Engineering Marvel at a Glance:

Dimensions: With a diameter of 13.6 meters, the cutterhead is designed to excavate a single tunnel large enough to accommodate both the up and down lines of the high-speed corridor.

• Its 350-tonne weight is equivalent to approximately 250 passenger cars (midsize SUVs).
• Arriving in five separate shipments, the unit was joined on-site using 1,600 kg of high-precision welding.
• The unit is equipped with 84 cutter discs, 124 scrapers, and 16 bucket lips to efficiently cut and remove muck during excavation.

Cutting discs are the main tools which cut through the rock face, followed by scrapers that are positioned on the cutterhead. Their primary function includes muck clearance at the face.

The bucket lip is the opening in the cutterhead through which muck enters the muck chamber of the machine. It helps in collection and directing the flow of muck onto the pipeline system for removal from the tunnel.

This TBM will start its journey of approximately 6 km from Vikhroli and head towards Bandra Kurla Complex under dense city landscape and the Mithi River before being retrieved at the under-construction Mumbai Bullet Train station at BKC.

Various monitoring instruments are being used to ensure safe excavation of the tunnel and all nearby structures. These include Surface Settlement Points (SSP), Optical Displacement Sensors (ODS) or tilt meters, BRT (By Reflect Target/3D Targets), strain gauges for monitoring micro strains in tunnel surfaces, and seismographs for monitoring Peak Particle Velocity (PPV), vibration, and seismic waves.