Railway Minister Ashwini Vaishnaw will inaugurate the underground tunnel-boring operation from Vikhroli to the Bandra Kurla Complex station on Sunday, marking the first use in India of a Tunnel Boring Machine (TBM) for the Mumbai-Ahmedabad High-Speed Rail Corridor. The machines, two customised German-made TBMs imported from China in March 2026, are owned by Afcons Infrastructure Limited (Afcons), which is constructing a 20.37 km tunnel including a seven km undersea stretch. The tunnel will be built at a depth of about 65 metres below ground level. An official of the National High Speed Rail Corporation Limited (NHSRCL) said the Railway Minister would push a button to commence the operation of a TBM stationed 56.6 metres below ground at Vikhroli. The first TBM will begin tunnelling from Vikhroli towards the BKC station, covering a distance of approximately five point eight km. A second TBM is being assembled at Sawli and is expected to be ready within a week; it will excavate the nine point seven km stretch from Sawli to Vikhroli, including the seven km undersea section. A senior railway expert said each TBM is expected to excavate about 300 metres of tunnel every month, and that once both machines become operational around 600 metres of tunnelling will be completed monthly. The 20.37 km package stretches from BKC to Shilphata, of which 15.4 km between BKC and Sawli will be excavated using TBMs while the remaining four point eight km from Sawli to Shilphata has already been completed using the drill-and-blast method. The tunnel will be a single-tube structure designed to accommodate twin tracks for bi-directional traffic. Two shafts at Vikhroli and Sawli, at depths of about 56 metres and 39 metres respectively, will facilitate construction, and 39 equipment rooms at 37 locations will be built adjoining the tunnel alignment. The TBMs are among the largest and most expensive deployed in India, each with a cutter head diameter of 13.6 metres. By comparison, TBMs used for urban metro projects typically have cutter head diameters of five to six metres.