Tunnel breakthroughs stack up, from Toronto’s Ontario Line to Mumbai’s Coastal Road

A nearly 23-foot tunnel boring machine has broken through into its first station under downtown Toronto; its twin is due to punch through beside it in December.

blogTO described the breakthrough as one of the Ontario Line’s biggest milestones so far, and it is not alone. Dubai opened a separate 1.65 km road tunnel linking Infinity Bridge to Deira, while Indian projects from Indore to Mumbai reported their own tunnel records.

How a cutterhead becomes a lined tunnel

The Toronto machine did not just grind forward. As it cut about 4,265 feet, crews lined the tunnel behind it with precast concrete rings; roughly 780 rings make up that progress. Indore Metro’s underground project shows the same sequence at a smaller scale: workers installed 11 precast concrete tunnel rings in one day, past a usual target of eight to nine, and completed 90 metres of tunnelling before Minister Kailash Vijayvargiya inspected the site. For instance, Toronto’s 780 rings over 4,265 feet works out to about one ring every five feet, while Indore’s single-day count beat its normal target by two to three rings.

Bigger machines and manufacturers circling in

India is now ordering machines at the top of the global size range. The Indian Express reported that Mumbai will get India’s largest tunnel boring machines in January, with tunnelling due to begin by May 2027. The 15.6-metre-diameter machines will bore 3.9 km twin tunnels 40 metres below ground between Malad’s Mindspace and Kandivali’s Charkop for the Coastal Road North project.

In Mumbai’s Thane–Borivali tunnel work, the first TBM, Nayak, has been commissioned and MEIL is set to begin operations with the second machine, Arjuna, for the twin tunnel project. The supplier field is widening at the same time: Mint reported that Larsen and Toubro is exploring at least half a dozen new businesses, including tunnel boring machines, nuclear fuel rods, rockets, and drones and their components.

Metro deadlines and mountain links

Chennai Metro Rail Ltd expects to complete the Panagal Park-Nandanam-Boat Club tunnel by the end of this month, tightening Phase II reach for commuters travelling to T. Nagar, Nandanam and Boat Club. In Uttarakhand, Chief Minister Pushkar Singh Dhami inspected a ₹156-crore bridge-tunnel project in Rudraprayag that is meant to improve connectivity between the Kedarnath and Badrinath national highways.

The older end of India’s tunnel spectrum is a hand-dug passage in Keralam: built in 1985 with basic tools for ₹10,000, the 40-metre underground route cut a 20-minute journey to farmland to three minutes, ETV Bharat reported.

When do road tunnels turn into legal battles?

Road tunnels are drawing immediate scrutiny because of traffic stakes and land costs. Dubai’s new Infinity Bridge-Deira tunnel is open and is rated for 12,000 vehicles an hour across its 1.65 km. Bengaluru is heading the other way, at least for now. A proposed 28-km extension of the East-West Tunnel Road to NICE Road carries six entry-exit points and is projected to ease congestion, improve cross-city connectivity and lift real estate prospects in western Bengaluru.

Bengaluru’s Hebbal tunnel hit a legal wall: the NGT halted felling of 1,128 trees until December 15 after more than 1,500 public objections, with IISc experts warning that the tunnel will merely shift traffic congestion rather than remove it. In Shimla, the high court has told NHAI to justify dropping a surface highway plan for a twin tunnel project and to say who would bear the ₹600 crore public-exchequer loss tied to land compensation payments.

The dates to watch are December for Toronto’s twin breakthrough, the end of this month for Chennai’s Panagal Park-Boat Club tunnel, and December 15 for the Bengaluru tree-felling pause.