In May 2017, the giant tunnel boring machines (TBM) machines that have been quietly boring underneath the city and creating tunnels for the Chennai Metro Rail for four years will have completed their task.
Officials of Chennai Metro Rail Limited (CMRL) said over 90 per cent of the tunnelling was complete and the remaining would be over in six months.
Eleven TBMs arrived in the city four years ago from across the world and started tunnelling work. But only five remain now and the rest have been sent back since the tunnelling is over.
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“Of the 24-km underground network, we had to tunnel for nearly 18 km, The remaining 6 km fall under the stations and is not executed by the TBMs. The TBMs have bored for about 16 km so far. The soil conditions have been hard to predict. In some areas, we had to bore through hard rock, while in others, it was mixed soil. Sometimes, loose soil gave way and that led to caving of road surfaces in various places,” an official said.
In 2010 and 2011, Chennai Metro Rail awarded contracts to companies including Gammon India and Mosmetrostroy (for design and construction of seven stations along Anna Salai), L&T and SUCG (for design and construction of stations along Poonamallee High Road) and Afcons Infrastructure Limited and Transtonnelstroy (for design and construction of stations in north Chennai and Poonamallee High Road).
But the project faced a major setback when the tunnelling came to a grinding halt in Anna Salai. This was because Mosmetrostroy abandoned the project and subsequently, CMRL terminated the contract of its joint venture partner Gammon India. Months later, the contract was awarded to L&T and Afcons Infrastructure Limited for station and tunnelling work.
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