The giant tunnel boring machines (TBMs) will begin burrowing beneath the city’s surface from Sunday to create another infrastructure lifeline for the city after Chennai Metro Rail Chairman and Union urban development secretary Sudhir Krishna pressed the button to kickstart the operations at the Nehru Park.
The ceremony to launch the tunneling work was a low-key affair in the wake of mishap at the metro rail site on Thursday when a 50 tonnes scaffolding collapsed on the busy 100 feet road between Koyambedu-Vadapalani stretch.
“Today, it was just an opening ceremony. From Sunday, the tunnel boring machines (TBMs) will begin drilling,” a metro rail spokesman said.
The tunneling between Nehru Park to Egmore is 939 meters and the distance is expected to be covered in about five months, CMRL sources said. Interestingly, the tender for design and construction of 3.342 km of twin tunnels including three underground stations at Nehru Park, Kilpauk Medical College, and Pachiappa’s College has been awarded to Larsen and Toubro, in joint venture with Chinese firm Shanghai Urban Construction Group (SUCG).
Initially, two TBMs will be operated under the guidance of experts in both the shifts with automatic alignment and monitoring control system developed with Japanese technology. The tunneling will be requiring feeding of segments brought from casting yard for installing the concrete linings of the twin tunnels.
“The cut soil will be brought out and disposed. All the necessary precautions with regard to the plugging of old bore wells and utility diversions have been taken well in advance and all the buildings enroute will be monitored round the clock when TBMs are in operations,” CMRL said.
He said heavy circular concrete liners used for the tunnels are manufactured at the state of the art Segment Casting factory at Vayalanellur, which has so far produced 1400 segment rings. “There will be cross passages between the two tunnels every 245 meters for ensuring operational fire safety,” he said. s are progressing now, CMRL sources said.
Metro rail is using 11 TBMs, each costing Rs 60 crore, assembled at specific sites to drill 24 km with 19 stations beneath the city to create infrastructure for its two corridors.
An L&T official, who is involved in the tunneling operations, said each day the machine will drill about six metres based on the soil condition.
“Initially, a workforce of 15-20 workers, including Chinese workers will be involved in the drilling operation which will be expanded. Chinese labourers are being used as they are specialized in operating Tunnel Boring Machines (TBM),” the L&T source said
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