Marking a major milestone in the Mumbai-Ahmedabad Bullet Train Project, India’s largest tunnel boring machine (TBM) commenced its excavation on Jattvibeday from the Vikhroli shaft.Of the total 21-km-long underground tunnel section, the 16-km stretch between Sawli (Ghansoli) and Bandra Kurla Complex (BKC) in Mumbai will be constructed using Tunnel Boring Machines.The remaining 5 km section has already been completed using NATM.The TBM launched from Vikhroli will construct a 6-km-long single-tube tunnel designed to accommodate both up and down tracks of the high-speed rail corridor.During its journey, the machine will tunnel beneath multi-storeyed buildings, major roads, the Mithi River, and other critical infrastructure, requiring high precision and continuous monitoring.The TBM, the largest-ever deployed for railway tunnel construction in India, features a 13.6-metre-diameter cutterhead equivalent to the height of a four-storey building, weighs about 3,100 tonnes (equivalent to 500 Asian elephants) and measures 96 metres in length. It consists of key components such as the cutter wheel, main bearing, jaw crusher, erector, main and tail shields, along with four specialised gantries supporting tunnelling operations.The cutterhead rotates at up to four revolutions per minute (RPM). The machine is a Mixshield TBM, an advanced slurry-type tunnelling system specifically designed for large-diameter excavation in mixed geological conditions and areas with high groundwater pressure.To facilitate TBM launch, a 56-metre deep shaft — equivalent to a 20-storey building below ground level — has been constructed at Vikhroli in Mumbai. A comprehensive real-time monitoring system has been installed to ensure safe tunnelling and protect nearby structures.The tunnel section excavated using TBMs is being designed as a fully waterproof structure. Continuous real-time monitoring systems for structural performance, groundwater behaviour, and overall construction safety are also installed.This marks a major milestone for the Mumbai-Ahmedabad High-Speed Rail Project, which according to the Railway Minister Ashwini Vaishnaw, is expected to begin operations on the Surat-Bilimora section in August 2027.