Mumbai, May 17 -- India's largest cutterhead for a rail tunnel boring machine (TBM) has been lowered at Vikhroli in Mumbai for the Mumbai-Ahmedabad Bullet Train project, marking a major milestone in the construction of the country's first undersea rail tunnel, according to the National High Speed Rail Corporation Limited (NHSRCL).

The cutterhead, which has a diameter of 13.6 metres and weighs around 350 tonnes, marks the final stage in the primary assembly of the TBM's main shield. NHSRCL said the machine will be used for excavation of a section of the underground tunnel for the high-speed rail corridor.

"Two TBMs, each weighing over 3,000 tonnes, are currently being assembled to construct a 16 km portion of the 21 km Mumbai tunnel," th...