Boring Machines Advance on 21-km Mumbai–Ahmedabad Tunnel

Two tunnel boring machines have begun driving the 21-km underground section of the Mumbai–Ahmedabad high-speed rail corridor, including the 7-km passage beneath Thane Creek that will become India's first undersea railway tunnel. The National High Speed Rail Corporation Limited (NHSRCL), the state agency building the 508-km line, started both machines in July 2026 on separate sections of the alignment.

The numbers frame the engineering task. Roughly 16 km of the tunnel is being excavated using tunnel boring machines (mechanised cutters that carve a circular bore and erect segmental lining behind them). The remaining 5 km uses the New Austrian Tunnelling Method, a drill-and-blast approach that relies on the surrounding rock mass to carry part of the structural load. Depths along parts of the alignment range from approximately 25 to 57 metres below ground level. Both railway tracks will run inside a single tube.

What is happening under Thane Creek?

The first machine started excavation from Vikhroli towards Bandra Kurla Complex on July 5, 2026, on a 6-km drive. The second began at Sawli, near Ghansoli, and is heading towards Vikhroli on an approximately 10-km route that includes the full 7-km underwater stretch beneath Thane Creek. When the drives complete, the tunnel will link Mumbai's Bandra Kurla Complex — the corridor's southern terminus and principal business district — with Shilphata on the city's north-eastern fringe.

Progress on this section follows an earlier geological milestone. In September 2025, engineers achieved a breakthrough on a 4.8-km tunnel section between Ghansoli and Shilphata, a stretch NHSRCL had identified as one of the project's more difficult geological challenges. That breakthrough removed a constraint on the alignment's northern portal approach.

Where does the wider project stand?

The corridor itself is designed for a maximum operating speed of 320 kmph and will connect two of India's major economic centres across Maharashtra and Gujarat, passing through the Union Territory of Dadra and Nagar Haveli. Twelve stations are planned: Mumbai BKC, Thane, Virar, Boisar, Vapi, Bilimora, Surat, Bharuch, Vadodara, Anand, Ahmedabad and Sabarmati.

Physical progress stands at 62% overall, with more than 366 km of viaduct girders erected. Construction is advancing simultaneously on elevated viaducts, bridges, stations and supporting infrastructure. Japan is providing the project's technical and financial assistance, an arrangement that has shaped both the rolling stock specification and the civil engineering standards applied to the tunnel works.

What does this change for intercity travel?

The practical question is time and capacity. A 508-km corridor built for 320 kmph operation compresses a journey that conventional rail covers in several hours, and the tunnel's single-tube, twin-track design allows bidirectional service without a second bore, which cuts both construction cost and land acquisition in Mumbai's dense urban fabric. The undersea alignment itself avoids surface routes through built-up Thane and Navi Mumbai, where land constraints make an elevated or surface line impractical.

NHSRCL's figures are measured results for works completed — the 4.8-km breakthrough, the 366 km of girders, the 62% physical progress. The 2027 date for the first operational section, flagged by Railway Minister Ashwini Vaishnaw, remains a projection that depends on the pace of the remaining tunnel drives, and the Thane Creek passage is widely regarded as the schedule-critical element of the whole corridor.

Planning is already looking beyond this line. NDTV Profit reports that Uttar Pradesh and Bihar feature on subsequent bullet train maps, with travel-time assessments under way for Lucknow, Varanasi and Patna. For now, the two boring machines working towards each other beneath Mumbai's eastern suburbs and the creek floor will determine how quickly India's first high-speed railway can begin carrying passengers.