India’s biggest TBM begins tunnelling for Mumbai coastal road

Maharashtra CM Uddhav Thackeray formally inaugurated the tunnelling work this week for India’s biggest tunnel boring machine (TBM) by Larsen & Toubro (L&T) for the twin 1,920 m tunnels between Priyadarshini Park and Chowpatty. This will be a short segment in Mumbai’s 29.2 km Coastal Road (Western Freeway) project.

TBM Mavala, a slurry machine, having a diameter of 12.19 m, which was commissioned last week for carrying out the tunnelling work, has since built at least three tunnel rings.

India’s biggest TBM has been named ‘Mavala’ after the infantry warriors in the army of Maratha warrior king Chhatrapati Shivaji. The TBM will be deployed to dig 3.4 km long tunnels as part of the coastal road project – a 22.2 km long freeway that would run along Mumbai’s western coastline, connecting Marine Lines in the south to Kandivali in the north.

The machine has been manufactured by China Railway Construction Heavy Industry Co. Ltd. (CRCHI) and arrived in Mumbai’s Priyadarshini Park neighbourhood in April 2020.

Assembly works on the TBM commenced in September and its shields, including an Indian-flag themed cutter head, were lowered into the ramp one by one in December 2020.

Each tunnel of this section (MCRP’s 3.93 km Package-4) will be 12 metres wide and comprise two lanes and one emergency lane. The TBM will operate 25 meters below the surface at Girgaum and 75 meters below Malabar Hill.

The BMC has completed over 20% work on the 10.5 km coastal road project, estimated to cost Rs 12,721 crore. So far, Rs 1,300 crore has been spent on the construction work.

L&T plans to excavate 9 m per day for the next 18 months to complete both tunnels by their internal deadline of June 2022.

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