India's largest rail TBM starts digging the bullet train's Vikhroli-BKC tunnel

The Mumbai-Ahmedabad high-speed rail project crossed a visible threshold on Sunday: the country's largest rail tunnel boring machine, a 13.6-metre Mixshield, began excavation at Vikhroli for the 5.8-km drive to the underground Bandra Kurla Complex terminus. A formal flag-off by Railway Minister Ashwini Vaishnaw was called off amid heavy rain, but the ministry ordered work to start immediately rather than wait for a fresh date.

A second machine, under assembly at Sawli in Thane district, is expected to be ready within days. It will bore the 9.7-km stretch towards Vikhroli that includes the 7-km section under Thane Creek, which would be India's first undersea rail tunnel. Between them, the two machines account for most of the roughly 21-km underground approach between BKC and Shilphata; the balance is being mined conventionally.

For MMR property watchers the milestone matters on two counts. It hardens the case for BKC's next decade, since the terminus anchors a district that already commands some of India's priciest office stock, and it keeps attention on the Vikhroli-Kanjurmarg belt, where large private land holdings sit directly on the alignment.

Timelines still depend on how the machines cope with basalt and creek-bed geology. But after years in which the Maharashtra section trailed Gujarat's viaducts, tunnelling at Vikhroli is the clearest sign yet that the Mumbai end is catching up.