India’s biggest TBM begins tunnelling for Mumbai coastal road

Maharashtra Chief Minister Uddhav Thackeray formally inaugurated the tunnelling work 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 in Mumbai. This will be a short segment in Mumbai’s Coastal Road (Western Freeway) Project (CRP).

TBMs are the major equipment used in tunnelling of bigger diameter tunnels, especially for underground metro and water pipelines, while micro tunnelling is used in laying smaller diameter tunnels. TBMs can complete work more efficiently and help minimise disruption.

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 CRP—a 22.2-km 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. (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.

The TBM approximately weighs around 1,500 million tonne and has been transferred to the launch site using a 200-wheel propeller. The machine was brought to India in May 2020, due to its large size it was dismantled in smaller parts and was brought to the launch site in 17 trucks.

The TBM will operate 25-m below the surface  at Girgaum and 75-m below Malabar Hill. The estimated cost of the project is Rs.127.21 billion. 

So far, Rs.13,000 million has been spent on construction work.

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