CMRL tunneling not so easy with Chennai’s geology

C Shivakumar

Chennai:

The geology of Chennai is giving sleepless nights to engineers who are work day and night to build the underground passage for Chennai Metro Rail.

Chennai Metro Rail General Manager (construction) V Somasundaram says the underground stretch is a challenging task for engineers as the ground is mixture of soil and rock unlike other metros where the ground is either soil or rock.

“In Delhi metro, it is totally soil but in Chennai it is both soil and rock which is posing a big challenge for tunnel boring machines.

He said the stretch between Washermenpet and Mannadi was totally soil as such the tunnel boring machines burrowed smoothly. The overhauling and repairing of tunnel boring machines was done only once.

However, the same could not be said of the stretch between Nehru Park and Egmore. This stretch is half rock and half soil posing a huge problem for the tunnel boring machines. “The TBMs were overhauled and repaired two times. And we expect it to be overhauled two times again soon,” says Somasundaram.

The other major is issue is the presence of water. The underground stretch is full of water and this is also posing one of the challenges, he says.

But will this delay the work in the underground stretch. “No” says Somasundaram. He says that Metro Rail has already taken all these issues before starting the work. “We have zeroed in on 10 metres of average speed per day,” he says. “Sometimes, we will be going at a speed of 15-20 metres and at times only five metre. These all have been factored in the schedule,” he says.

Meanwhile, the first tunnel boring machine from Washermenpet and  Mannadi has completed the 1341.2 metre drive and reached Mannadi while the second tunnel boring machine in the same stretch has completed 203 metre drive.

Similarly, the tunnel boring works from Nehru Park to Egmore Metro is in progress. The first TBM has completed 360m while the second TBM has completed 475 metres.