Tunnelling work at the Nehru Park Metro Rail site has been progressing well despite challenging soil conditions, officials of Chennai Metro Rail Limited (CMRL) said.

With two tunnel boring machines (TBMs) from China shipped to the country in December, 2011 — as part of an agreement between CMRL, joint venture partners Larsen and Toubro and Shanghai Urban Construction Group — this site was the first to begin tunnelling work in July 2012.

At present Metro Rail uses 11 TBMs at various sites across the city. The machines tunnel passages that will eventually connect underground stations.

The first TBM at the Nehru Park site that began tunnelling in July has completed 565 metres and the second one, which started in October, has drilled 455 metres. The two machines still have 939 metres to tunnel through from Nehru Park station to Egmore station, a CMRL official said.

“We have finished construction of the diaphragm walls of the station. Platform work is currently in progress. Of the four entry and exits that the station will have, we are building one right now and the other three will soon be completed,” he said.

The TBMs are drilling about 8-10 metres a day. However, this varies depending upon soil condition, the official said.

“Soil conditions here are very unpredictable and it is quite challenging to tunnel this stretch. Sometimes it is very rocky and this slows down tunnelling work. On some days, conditions are favourable and work progresses fast,” said another official.

Sources said that it may take another six months for tunnelling work to be completed at this station. Underground station work is expected to be completed by April 2015.

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