Chennai Metro on Anna Salai
While riding through Anna Salai you know the workers boxed up inside Metro Rail’s iron sheets are up to something big but couldn’t take a peek. Here is the update from behind the iron wall: Metro has begun underground stations work at three spots along the stretch. Of the seven underground metro stations that will come up beneath Anna Salai, work has begun on the new secretariat campus station, LIC station and Thousand Lights station.
Traffic has been diverted on the LIC and the LLA sides of the arterial road to make space for heavy machinery that will burrow trenches for underground stations. If you are already fretting over the traffic squeeze, then make sure you have enough patience in reserve to bear it for a year.
An underground station evolves through various stages – first the soil is tested, cables and pipelines are shifted, diaphragm walls are built to shore up dug-up earth and finally, the construction of station begins. As the stations are built after cutting open the road surface, metro rail has decided to slash open one portion of the road, complete the works, cover it up and move over to the other half.
Metro has started making diaphragm walls for new secretariat, LIC and Thousand Lights stations. The wall is needed to hold up the earth from collapsing when excavation begins. Raising of the walls requires the help of steel behemoths. Giant drills will make a deep trench, then cranes are used to hoist and place the cylindrical rigs in the trench and concrete is poured to fill up the trench that contains the rigs.
Giant cranes have been moved to the new secretariat station work site while drills have been moved to LIC and LLA. Soil excavation will begin soon after the walls are ready. Water pipelines and power cables are being moved at DMS for Gemini metro station, and Nandanam.
Imagine a five-storey building under the ground — that’s how tall an underground station will be. The roof will be three to four meters below the road surface. Power cables and pipelines shifted out during construction will be put back in this place. Concourse area, where commuters will buy tickets, will be six metres below the roof and six metres further down will be the platform.
The deepest point of an underground station will be 17 metres below the road. It may vary marginally. We have taken care not to increase the depth further,” said an official.