The first tunnel boring machine (TBM) launched in Chennai at Nehru Park for Metro Rail underground work has completed its first tunnel.

The TBM—which used to excavate tunnels to connect the underground stations—had to tunnel from Nehru Park to Egmore, a distance of 948 metres. It was launched in July 2012.

“The TBM reached Egmore station last week. The other TBM has so far completed about 720 metres and it may be a while before it arrives at Egmore. Simultaneously, the assembling of another TBM that will tunnel from Pachaiyappa’s College station to Kilpauk has commenced,” said an official of Chennai Metro Rail Limited (CMRL).

The two TBMs employed in this station have been shipped from China and the Chinese workers too are here to operate these machines as part of a MoU signed between CMRL and joint ventures, Larsen & Toubro and China-based Shanghai Urban Construction Group.

The TBMs are usually operated at a speed of 6-10 metres a day and the soil conditions play an important role in determining the speed of the TBM. If the soil is loose, then the speed of the TBM may be reduced, according to officials.

The Chennai Metro Rail built at a cost of Rs. 14,600 crore will dot 45 km of the city. Of the 32 stations, 19 will be underground and the rest 13 elevated.

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