Mumbai's relentless heavy rainfall on Saturday, July 5, 2026, forced the postponement of the formal inauguration for the underground tunnel-boring work on the ambitious Mumbai-Ahmedabad bullet train project. However, the Railway Ministry swiftly intervened, directing authorities to commence the critical excavation immediately to prevent any further delays to India's first high-speed rail corridor.
The formal launch, which was to be presided over by Railway Minister Ashwini Vaishnaw, was scheduled to take place on Sunday. It would have marked the maiden deployment of a tunnel boring machine (TBM) for the project, specifically for the section connecting Vikhroli to the Bandra Kurla Complex (BKC) station. Despite the weather-induced ceremony cancellation, the National High Speed Rail Corporation Limited (NHSRCL) was instructed to proceed without the official event.
Advanced Tunneling Begins for Bullet Train
Afcons Infrastructure Limited, the firm responsible for executing the underground segment, has been tasked with initiating TBM operations promptly. The project involves two specially designed German-made TBMs, which were imported from China in March 2026. These machines are integral to constructing a significant 20.37-kilometre tunnel, which includes a challenging 7-kilometre undersea stretch.
The tunnel, designed to accommodate twin tracks for bi-directional train movement, will run at an approximate depth of 65 meters below ground level. Its overall length extends from the BKC station to Shilphata. Of this, 15.4 kilometres between BKC and Sawli will be excavated using these advanced TBMs, while a 4.8-kilometre portion from Sawli to Shilphata has already been completed using the conventional drill-and-blast method.
Massive TBMs Tackle Complex Route
The TBMs employed for this project are notable for their scale, featuring cutter-head diameters of 13.6 meters. This makes them among the largest and most costly heavy machinery ever deployed in Indian railway infrastructure, far exceeding the 5 to 6-meter diameters typically seen in urban metro tunneling projects.
The first TBM is designated to bore a 5.8-kilometre section from Vikhroli to the BKC station. The second machine, currently undergoing assembly at Sawli, is anticipated to be operational within a week. It will then tackle the 9.7-kilometre stretch from Sawli to Vikhroli, which encompasses the critical 7-kilometre undersea segment.
Each TBM is projected to excavate approximately 300 meters per month. Once both machines are fully operational, the combined tunneling progress is expected to reach around 600 meters monthly, accelerating the construction of this vital high-speed rail link between Maharashtra and Gujarat.
Supporting the construction efforts are two shafts, located at Vikhroli and Sawli, with depths of about 56 meters and 39 meters respectively. The project package also includes the development of 39 equipment rooms across 37 locations adjacent to the tunnel, ensuring comprehensive operational support for the ambitious undertaking.