A 21-km-long underground/undersea tunnel is being constructed between the Mumbai-Ahmedabad bullet train station at Bandra-Kurla Complex (BKC) and Shilphata in Maharashtra. Of this 21 km, 16 km will be built using tunnel-boring machines (TBM), while the remaining 5 km will be constructed using the New Austrian Tunneling Method (NATM). This includes a 7-km undersea tunnel at Thane Creek.

The construction work for the Mumbai-Ahmedabad bullet train has made significant progress across various locations. At ADIT (Additionally Driven Intermediate Tunnel) portal, a 394-metre-long tunnel was completed last May in a record time of six months. This has facilitated two additional NATM faces for excavation, in addition to the Shilphata site. As a result, 1,111 metres of tunnelling work has been achieved so far, with 622 metres completed towards BKC and 489 metres towards Ahmedabad. ADIT, which measures 11x6.4 metres, will provide direct vehicular access to the main tunnel during both construction and operations and could also be used for emergency evacuations if necessary.