Five years ago, the first tunnel boring machine (TBM) arrived from China and began to create tunnels for the underground Chennai Metro Rail work. This May, after building tunnels for 24 km in the city, the TBMs would have finished their job.
So far, the tunnelling work is complete in all stretches barring just two.
According to officials of Chennai Metro Rail Limited (CMRL), about 150 metres of tunnelling from Rajiv Gandhi Government General Hospital to Chennai Central and 1.6 km from Thousand Lights to Gemini have to be finished.
“The soil conditions were challenging in a lot of places, which delayed the tunnelling work. In Anna Salai, there was hard rock first which was very difficult to bore through but now, it is top soil and much easier to handle. In the other stretches, work including laying of tracks and construction of cross passage (a safety passage for passengers inside tunnels) is in progress,” an official said.
A total of 12 TBMs arrived in the city when the work started and workers from China, Germany, South Africa and Russia were part of the underground project. But now, only three TBMs are at work and only a few South Africans and Germans remain engaged in the work.
Of the 45 km of phase I of the Chennai Metro Rail project, 21 km are elevated and the remaining 24 km run underground. Officials said construction of the underground network costs more than the elevated strtech; building one km of underground tunnel costs around Rs. 300-400 crore, an official said.
The first underground stretch from Thirumangalam to Nehru Park is expected to open by April this year.
