Assembly of tunnel boring machine for Mumbai-Ahmedabad bullet train project begins

The lowering and assembly of the tunnel boring machine (TBM) has commenced for the construction of a 16 km-long tunnel through TBM between Bandra Kurla Complex (BKC) and Sawli (near Ghansoli) in Maharashtra for the Mumbai-Ahmedabad Bullet Train Project, National High Speed Rail Corporation Limited (NHSRCL) officials said on Thursday.

The 21 km-long tunnel is being constructed for the project between BKC and Shilphata in Maharashtra. The tunnel also features India’s first seven km-long undersea tunnel beneath Thane Creek. Out of 21 km, 5 km of tunnel using the New Austrian Tunnelling Method (NATM) is already completed and the remaining 16 km will be completed through Tunnel Boring Machines (TBM).

The tunnel will be a single tube tunnel of 13.1 m diameter to accommodate twin track. This tunnel will be about 25 to 57 metres deep from the ground level and the deepest construction point will be 114 metres below the Parsik Hill.

The process began with the lowering of one of the six segments of the main shield, weighing approximately 170 metric tonnes. This segment measures about 8.66 metres in length and approximately seven metres in width and was lowered at a depth of 56 metres below ground level, equivalent to a 20-storey building, at Vikhroli.

“Two TBMs are being used and the tunnelling operations will commence following comprehensive testing and commissioning,” officials said.

To lower the TBMs, three shafts have been constructed: a retrieval shaft at BKC, and shafts at Vikhroli and Sawli (near Ghansoli). “TBM 1 will start from Shaft 2 at Vikhroli and will move towards Shaft 1 of Mumbai Bullet Train station at BKC while TBM 2 will start from Shaft 3 at Sawli and move towards Vikhroli,” officials explained.

The two TBMs, weighing 3,080 tonnes (TBM-1) and 3,184 tonnes (TBM-2) respectively, are among the most advanced tunnelling machines deployed in the country. These advanced TBMs, based on Mix Shield or Slurry technology, are specifically designed to operate in complex geological conditions.

Each TBM measures 95.32 metres in total length and comprises several critical components, including the cutter wheel, main bearing, jaw crusher, erector, main shield, tail shield, and four specialised gantries that support tunnelling operations.

These machines can operate at a maximum cutter head speed of four RPM (revolutions per minute), with a maximum excavation rate of 49 mm per minute, enabling steady and controlled tunnelling progress while maintaining high safety standards, officials added.