The Hindustan Times reported that BMC (Brihanmumbai Municipal Corporation) is set to start tunnel boring on the Mumbai Coastal Road Project by October 25. The length of the twin tunnels is 3.4km and they form part of the Coastal Road between Priyadarshini Park at Malabar Hill and Girgaum Chowpatty.
The TBM operation is predicted to take between eight to ten months to complete both tubes which run through a tough geology containing basically basalt of 200MPa maximum compressive strength. The 12m-diameter tunnels are going to have three traffic lanes and will lie at depths of between 25 to 70 meters underground. A section of the alignment between Malabar Hill and Girgaum will run under the sea.
Reception and launch shafts at both ends of the parallel tubes have been completed. After arriving on site in April in 17 truckloads, at the present, the TBM is being partially overhauled above ground after which it will be lowered for the completion of the final assembly stages underground.
It is expected from the Chinese-made CRCHI machine to take nearly four to five months to excavate each tube, beginning from Priyadarshini Park, boring the length of one tube, then pulled out at Girgaum Chowpatty to be taken back to Priyadashini Park to begin the second tube. BMC evaluates that the TBM is going to bore nearly 3 meters per day, with a total excavation time of 276 days to complete the tunnels’ excavation.
Heretofore, about 16% of the Coastal Road Project has been completed; it is expected to have the full completion by July 2023.