Chennai Metro Rail’s phase II will have stations on three levels

Pattalam, Kutchery Road, Alwarpet and Bharathidasan Road will have underground stations with stacked tunnels, one above the other, due to space constraints, CMRL officials said

November 16, 2022 04:44 pm | Updated 04:44 pm IST - CHENNAI

Tunnel boring machines will create two tunnels, one above the other, for these stations, an official said.

Tunnel boring machines will create two tunnels, one above the other, for these stations, an official said. | Photo Credit: JOTHI RAMALINGAM B

Commuters of Chennai Metro Rail (CMRL) are accustomed to witnessing trains making a stop on either side of the platform. Now, at some stations in phase II of the project, the two tracks (up line and down line) will be at two different levels, owing to a lack of available space, CMRL officials have said.

At Pattalam, Kutchery Road, Alwarpet and Bharathidasan Road, which will be built as underground stations, commuters will have to purchase tickets on the first level (concourse level) and may board the trains at the upper track or lower track, depending on the final construction.

“It will be challenging during the construction as we will have to build stacked tunnels at these four locations,” a CMRL official said. Stacked tunnels are those when two tunnel boring machines (TBM) create two tunnels, one above the other, and this is being done due to space constraints, he said.

“Normally, the tunnels will be built on either side of the platform and hence, during operations, the trains will arrive and leave on [either] side of a platform. But at these locations, the road width is as narrow as 10 metres. So, we decided to build tunnels vertically, with one above and one below,” another official said.

While the upper track will be constructed 14.7 metres below the ground, the lower one will be located at a depth of 28.5 metres. “In case of stacked tunnels, the lower tunnel will be bored first and after a gap of 90 days, the upper tunnel will be built. We have to take precautionary measures to gauge the vibrations and safety of the road and the old vulnerable buildings that are situated within the tunnelling zone,” the official noted.

Of the four stations, three — Pattalam, Kutchery Road and Alwarpet — will fall under Corridor 3 that stretches from Madhavaram to SIPCOT covering 45.8 km. Bharathidasan Road will be covered under Corridor 4 from Poonamallee to Light House which spans 26.1 km.

Thirumayilai Metro Rail station, which will come under Corridor 3, too will be built with stacked tunnels but it has four levels and will be the deepest station. With three platform levels and a concourse or ticketing level, the station goes as deep as 35 metres below the ground.

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