The Zaroli mountain tunnel, a crucial part of the Mumbai–Ahmedabad High-Speed Rail (MAHSR) corridor, is nearing completion, the National High Speed Rail Corporation Limited (NHSRCL) announced. NHSRCL is the implementing agency for the 508-kilometre bullet train project connecting Mumbai and Ahmedabad.Located about one kilometre from Zaroli village in Umbergaon taluka of Gujarat’s Valsad district, this tunnel is the first and only mountain tunnel constructed in Gujarat as part of the MAHSR project. Measuring 350 metres in length, it features a single horseshoe-shaped tube with a cross-sectional diameter of 12.6 metres and a height of 10.25 metres.The tunnel was constructed using the New Austrian Tunnelling Method (NATM), which involved drilling, controlled blasting, muck removal, and structural support with shotcrete, steel ribs, lattice girders, and rock bolts. Despite complex geological conditions, the breakthrough was achieved in October 2023, just ten months after excavation began.Designed to house twin Shinkansen-style tracks, the tunnel will enable trains to travel at speeds of up to 350 kilometres per hour. Precise alignment and geometry were essential to meet the high-speed operational requirements.Zaroli is the first of eight mountain tunnels planned on the MAHSR route. While Zaroli lies in Gujarat, the other seven tunnels are located in Maharashtra’s Palghar district. This includes a 21-kilometre underground segment with India’s first undersea rail tunnel beneath Thane Creek.Significant progress has been made across the entire 508-kilometre corridor. Over 304 km of viaduct and 388 km of pier work have been completed, alongside 15 river bridges, eight steel bridges, and five pre-stressed concrete (PSC) bridges. Approximately 163 track kilometres of track bed construction have also been finalised.Recently, NHSRCL launched the first full-span 40-metre Pre-Stressed Concrete (PSC) Box Girder at Sakhare Village, Dahanu, in Maharashtra’s section of the corridor.The Mumbai-Ahmedabad High-Speed Rail project will pass through Gujarat, Maharashtra, and the Union Territory of Dadra & Nagar Haveli. The corridor includes 12 planned stations at Mumbai, Thane, Virar, Boisar, Vapi, Billimora, Surat, Bharuch, Vadodara, Anand, Ahmedabad, and Sabarmati.