Meera Srinivasan hops across the offices of The Hindu on Anna Salai to chat up engineers toiling away at the site

In just a few years, I could be standing at the same spot — 20 metres below the ground — waiting to take a train back home. This thought came to my mind on Thursday morning as I walked into the construction site where Chennai Metro Rail Ltd is building the Government Estate metro station.

Gigantic machines, against the backdrop of the abandoned Secretariat complex, seem to be hard at work with a mind of their own, even as men sporting helmets in different colours walk around like Lilliputians. The engineers insist that the photographer and I wear the necessary ‘PPE' (personal protective equipment) — a helmet, safety jacket and shoes before proceeding on a guided tour of the site.

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Imposing machinery apart, makeshift tents, canteen, first-aid centre and toilets comprise the space inside the cordoned-off area. It is a town in itself and is inhabited by over a hundred workers, toiling away day and night.

One of the seven underground stations along Anna Salai, the Government Estate station will be connected to Chintadripet MRTS station nearby.

Engineering marvel

As senior engineers patiently explain the various processes involved in construction, often interrupted by rather basic questions from me, civil engineering suddenly seems like an exotic discipline.

Typically, work on any station begins with the diversion of the various utilities in the area — water pipes, sewer lines and telecom wires. With this work completed for the area under construction, the collective energy of nearly 100 people is currently focussed on building diaphragm walls.

“The wall, about 1 metre thick, will go as deep as 25 metres. The tracks for the metro will be laid at a depth of around 16 metres. The station, too, will be built at nearly that depth,” an engineer said.

To be erected on all four sides, the walls form an outer shell within which the station will be built. A total of 81 concrete panels, each 6.5 metres wide, will be used for the outer structure. So far, 30 panels have been cast underground.

Once the outer shell is complete, excavation work will begin to make way for the station within. The Government Estate station will have four entry-exit points, two on either side of Anna Salai.

Tunnelling ahead

Once considerable work on the station is complete, underground tunnelling work will be undertaken to connect different stations. As many as eleven Tunnel Boring Machines (TBMs) will be used to drill through the earth and form tunnels. “Five TBMs have already arrived from China by sea,” said the engineer.

Four TBMs have been allocated for the seven underground stations along Anna Salai. Two of them will be used for the Saidapet to Gemini stretch for the stations at Saidapet, Chamiers Road, Teynampet and Gemini. Two others will be used for the stretch from Gemini to Government Estate tunnelling stations at Thousand Lights, LIC and Government Estate.

Tunnelling work is likely to begin from the site at May Day park in September.

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Meera SrinivasanJune 28, 2012

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