National High Speed Rail Corporation Limited (NHSRCL) has successfully lowered the cutterhead of the second Tunnel Boring Machine (TBM) for the Mumbai-Ahmedabad bullet train project in Navi Mumbai, officials said on Sunday, reported the PTI.
The major engineering milestone was achieved at Sawli near Ghansoli on Saturday as part of the underground tunnel construction for the high-speed rail corridor.
According to NHSRCL, the 13.6-metre diameter cutterhead weighs around 350 tonnes and forms a critical part of the TBM’s main shield assembly.
The operation marks the final stage of the primary assembly process before the machine becomes fully operational.
The second TBM will tunnel from Sawli towards Vikhroli in Mumbai, while the cutterhead for the first Tunnel Boring Machine was lowered at Vikhroli last week, as per the PTI.
Excavation work expected from July
Officials said both TBMs will now undergo final assembly and commissioning trials before excavation work begins in the first week of July.
The machines are specifically designed to excavate a single large tunnel capable of accommodating both up and down railway lines of the Mumbai-Ahmedabad high-speed rail corridor, according to the PTI.
Advanced technology and heavy engineering
NHSRCL stated that each cutterhead is equipped with 84 cutter discs, 124 scrapers and 16 bucket lips, officials said.
These components help in excavation and the removal of debris during tunnelling operations.
The two slurry-based Mix Shield TBMs weigh 3,080 tonnes and 3,184 tonnes respectively, with each machine measuring over 95 metres in length.
The machines include several advanced components such as the cutter wheel, main bearing, jaw crusher, erector, main shield, tail shield and four specialised gantries.
India’s first undersea rail tunnel
According to the PTI, the TBMs are being assembled for the construction of a 16-kilometre section of the 21-kilometre Mumbai tunnel under the bullet train project.
The stretch includes a 7-kilometre undersea tunnel beneath Thane Creek, which will become India’s first undersea rail tunnel.
According to NHSRCL, the TBMs can operate at a maximum cutterhead speed of four revolutions per minute and achieve an excavation rate of up to 49 millimetres per minute while maintaining safety standards, the news agency reported.
(with PTI inputs)
