The National High Speed Rail Corporation Limited (NHSRCL) has said that the assembly of the second tunnel boring machine (TBM) has commenced at Sawli, near Ghansoli in Mumbai, as part of the underground works for the Mumbai-Ahmedabad High-Speed Rail corridor.
According to a statement by NHSRCL on Saturday, 11 April, this second TBM is being assembled at a depth of 39 metres below ground and will drive from Sawli towards Vikhroli.
NHSRCL is the implementing agency for the 508 km Mumbai-Ahmedabad bullet train project.
This development comes days after the first TBM components were lowered at the Vikhroli shaft on 9 April, marking the start of underground tunnelling preparations.
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.
At Sawli, a key component of the second TBM assembly, a gantry weighing 190 metric tonnes and measuring 18 metres in length, 10 metres in width, and 9 metres in height, has been lowered into the shaft.
Each TBM will be equipped with four gantries, which will be attached to the main shield assembly and cutterhead.
These gantries will move along the entire excavated tunnel length and support operations such as excavation, waterproofing, and installation of tunnel lining segments.
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NHSRCL stated that the assembly at Sawli is being carried out 39 metres below ground level under constrained conditions, requiring detailed planning and precision.
According to the agency, TBMs initial drive is expected to commence in July 2026.
This segment is part of a larger 21 Km underground alignment between BKC and Shilphata, which includes India’s first 7 Km undersea rail tunnel beneath Thane Creek.
NHSRCL had earlier stated that while 5 Km of tunnelling using the New Austrian Tunnelling Method (NATM) has already been completed, the remaining 16 Km will be executed using TBMs.
The two TBMs, weighing 3080 tons (TBM-1) and 3184 tons (TBM-2) respectively are most advanced tunnelling machines deployed in the country. These advanced TBMs, based on Mix Shield / 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 specialized gantries that support tunnelling operations.
These machines can operate at a maximum cutterhead speed of 4 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.
