The Mumbai Metro Rail Corporation (MMRC) on Tuesday received the first of the 17 Tunnel Boring Machines (TBMs) it has ordered for construction of the Colaba-Bandra-SEEPZ corridor, a top official said here.Costing Rs 80 crore and weighing around 700-800 tonnes, with a diameter of 6.4 metres, the 100-metre long machine will help in building a tunnel of 5.8 metres size, said MMRC Managing Director Ashwini Bhide.
Procured from the German manufacturer, Herrenknecht AG from its factory in China's Guangzhou, the machine is expected to be lowered from the launching shaft at Naya Nagar in Mahim around mid-October using heavy gantry of 135 tonnes capacity.Prior to that the different components of the machine including front and middle shields, cutter head, erector, screw conveyor and tail-skin shield will be assembled over a period of 45 days.The highly-mechanised Earth Pressure Balance device will be used to construct the tunnels with circular cross-section, said Bhide."The machine is one of the three TBMs to be used for constructing 6.10 km long tunnels between Dharavi and Siddhi Vinayak Metro stations with Shitla Devi and Dadar stations next month," she added.
With the arrival of the first TBM, the MMRC has kicked off its tunneling activity, the most critical part of this project."Over the next two years, a total of 17 TBMs shall be deployed constructing the 33.50 km long twin tunnels on the corridor," Bhide added.The Colaba-Bandra-SEEPZ line will be the first Metro stretch running fully underground and a 1.2 kms long stretch that would be constructed below the Mithi River-Mahim Creek.The project comprising 27 stations en route and estimated to cost around Rs 23,000 crore, is expected to be completed by 2020, to serve nearly two million passengers daily, as per plans.The precast segments essential for forming a concrete ring inside the tunnel are already being manufactured at six different casting yards.Around 40,000 segments rings will be needed for the entire project which will be casted in 65 moulds imported from France and South Korea, she said.The TBMs have been successfully used to bore similar tunnels in New Delhi, Kolkata, Chennai, Bangaluru and heritage precincts of Jaipur besides cities like Rome, Paris, Barcelona, Madrid, etc.