The formal launch of underground tunnel-boring work for the Mumbai-Ahmedabad Bullet Train project was postponed by the Railway Ministry on Saturday because of adverse weather conditions in Mumbai. The decision was taken after continuous rainfall was experienced in the city and red and orange alerts were issued by the India Meteorological Department (IMD) for the next couple of days. While the ceremonial launch was deferred, the National High Speed Rail Corporation Limited (NHSRCL) was directed to commence the work immediately so that the project would not be delayed.
The underground tunnel-boring work is being undertaken by Afcons Infrastructure Limited. It was stated by NHSRCL officials that tunnel boring machine (TBM) operations would now begin for the timely completion and launch of the Mumbai-Ahmedabad Bullet Train project. Railway Minister Ashwini Vaishnaw had been scheduled to inaugurate the underground tunnel-boring work from Vikhroli to the Bandra Kurla Complex (BKC) station in Mumbai. The event was to mark the first use of a tunnel boring machine in the country's first bullet train project.
The two customised German-made tunnel boring machines were imported via the sea route from China in March 2026. The machines are owned by Afcons Infrastructure Limited, which is constructing the 20.37-km underground tunnel, including a 7-km undersea section. The tunnel is being constructed at a depth of around 65 metres below ground level.
It was stated that the first TBM would begin tunnelling from Vikhroli towards the Bandra Kurla Complex station and would cover approximately 5.8 km. The second TBM is being assembled at Sawli and is expected to be ready within a week. It will excavate the 9.7-km stretch from Sawli to Vikhroli, including the 7-km undersea section.
Each tunnel boring machine is expected to excavate around 300 metres of tunnel every month. Once both machines become operational, around 600 metres of tunnelling will be completed every month. Officials stated that the 20.37-km tunnel extends from the Bandra Kurla Complex station to Shilphata. Of the total length, 15.4 km between BKC and Sawli will be excavated using TBMs, while the remaining 4.8-km stretch between Sawli and Shilphata has already been completed using the drill-and-blast method.
The tunnel is being constructed as a single-tube pathway that will accommodate twin tracks for bi-directional traffic. Two shafts at Vikhroli and Sawli, at approximate depths of 56 metres and 39 metres respectively, will facilitate construction. In addition, 39 equipment rooms at 37 locations will be constructed adjoining the tunnel as part of the package.
The TBMs have been described as among the largest and most expensive heavy machinery to be deployed in India. Each machine has a cutter-head diameter of 13.6 metres. By comparison, officials stated that TBMs used for urban metro rail systems typically have cutter-head diameters of 5 to 6 metres. The Mumbai-Ahmedabad High-Speed Rail Corridor spans 508 km and is intended to provide high-speed connectivity between Maharashtra and Gujarat.