The National High Speed Rail Corporation Limited announced that a second tunnel boring machine has begun digging from Sawli in Ghansoli toward Vikhroli in Maharashtra. This forms part of the Mumbai-Ahmedabad high-speed rail corridor. Within the 10-kilometre tunnel stretch, seven kilometres will run beneath Thane Creek, creating the nation’s first undersea railway passage.
The overall underground section spans 21 kilometres between Sawli and Bandra Kurla Complex in Mumbai. The first machine started its six-kilometre journey from Vikhroli toward Bandra Kurla Complex on July 5, 2026, while the remaining five kilometres were completed earlier using the New Austrian Tunnelling Method.
This machine ranks among the largest used for railway tunnels in India. Its cutterhead measures 13.6 metres across, roughly the height of a four-storey building. The unit weighs about 3,200 tonnes, comparable to nearly 500 Asian elephants, and extends 96 metres in length, similar to a football field.
Configured as a Mixshield slurry-type device, it employs pressurised bentonite slurry to stabilise the excavation face. The design includes continuous monitoring of structural behaviour, groundwater levels and safety. Double-layer EPDM gaskets together with hydrophilic seals protect the lining against water ingress, ensuring lasting durability.
