Mumbai: Tunnelling for the underground metro rail line between Colaba and SEEPZ is likely to be completed soon with the final tunnel set to see daylight sometime in the next seven days. This will be the 42nd and final breakthrough in the tunnel-boring works for the much-awaited metro.
“Our tunnel-boring machine Tansa-1 was launched in September 2020 from the Science Museum and covered 1,136 metres to reach Mahalaxmi in early 2022,” said Subodh K Gupta, Director (Projects), Mumbai Metro Rail Corporation. “The machine was relaunched in April 2022 to excavate the tunnel from Mahalaxmi to Mumbai Central.”
In the next few days, the machine is expected to emerge at Mumbai Central, marking the end of work using these heavy-duty machines. The tunnelling work is 99.7% complete, and only 15 or 20 segment rings are left to be fixed. The rings are made of concrete that is joined and put on the rock wall to hold up external pressure and provide a finish to the tunnel.
When it emerges at Mumbai Central, Tansa-1 would have covered 837 metres from Mahalaxmi. The MMRC and its contractors faced a challenge when Tansa-1 broke down during the pandemic and the main bearing of the machine that rotates the front cutters had to be replaced. The replacement had to be shipped from Singapore at a time when few cargo ships were sailing while the engineers who would fix it were in France and the machine’s controller was in the US.
The first breakthrough was achieved in September 2018 at Terminal 2 of the city airport after the tunnel-boring machine had covered 1.26 km from Marol Naka starting January 2018.
In June this year, the 41st breakthrough was achieved at Mumbai Central when Tansa-2 traversed the tunnel parallel to the one being dug by Tansa-1. It completed 832.5 metres of excavation in 282 days. For the engineers involved, this will be a long-awaited landmark marking the success of their efforts.
