India's largest tunnel boring machine (TBM) will begin excavation on Monday from the Vikhroli shaft towards the under-construction Mumbai Bullet Train station, marking a major milestone in the Mumbai-Ahmedabad High-Speed Rail Corridor.
According to the National High Speed Rail Corporation Ltd (NHSRCL), the TBM will excavate a 6-km-long single-tube tunnel designed to carry both up and down bullet train tracks. It forms part of the 21-km underground section of the project in Mumbai.
Of the total underground stretch, 16 km between Sawli (Ghansoli) and Bandra Kurla Complex (BKC) will be excavated using tunnel boring machines, while the remaining 5 km has already been completed using the New Austrian Tunnelling Method (NATM).
The Mixshield TBM, one of the largest ever deployed for railway tunnel construction in India, has a cutterhead measuring 13.6 metres in diameter, weighs about 3,100 tonnes and is 96 metres long. During excavation, it will pass beneath densely populated urban areas, including multi-storeyed buildings, roads, the Mithi River and other critical infrastructure.
The machine uses advanced slurry-based Mixshield technology, in which pressurised bentonite slurry stabilises the tunnel face during excavation. The system has been selected for Mumbai's challenging geological conditions and dense urban environment as it helps minimise ground settlement and surface disruption.
Also read: Bengal in line for bullet train under ₹1-lakh-crore rail plan
One of its key features is the ability to excavate the tunnel and install precast concrete segment rings simultaneously, improving both construction speed and operational safety.
To facilitate the launch, a 56-metre-deep shaft has been constructed at Vikhroli. The site is equipped with support infrastructure, including water and slurry treatment plants, bentonite storage facilities, a dedicated power substation, backup generators, a ready-mix concrete plant, sewage treatment systems and logistics infrastructure.
NHSRCL said a comprehensive real-time monitoring network has also been installed to ensure safe tunnelling and protect surrounding structures. The system includes surface settlement points, optical displacement sensors, tilt meters, bi-reflective targets, strain gauges and seismographs.
Meanwhile, an 11.17-hectare casting yard at Mahape in Thane district is manufacturing 77,000 precast concrete segments required to build 7,700 tunnel rings for the 16-km TBM section. Each tunnel ring comprises nine curved segments and one key segment, weighs around 100 tonnes, and is designed with double-layer EPDM gaskets and hydrophilic seals to ensure a fully waterproof tunnel structure.
Follow us
