BENGALURU: As Tunnel Boring Machine ‘Urja’ completed its complicated drilling task from Cantonment to Shivajinagar on Wednesday, it thrust its head out right into a special concrete box. The box was set up to ensure the safety of buildings in Shivajinagar.
The move to ensconce the machine in the box paid off, and Bangalore Metro Rail Corporation Limited (BMRCL) now plans to create such boxes for the eight other TBMs, when they near their destination. This is only the second time that such a box was created; the previous occasion was for Metro Phase-I line, when a machine drilled from South ramp to KR Market to create the underground corridor of the North-South Line.
The massive TBM from China has a diameter of 6.7 metres. A top BMRCL official told TNIE, “We created a special concrete block (false block) of length 15 metres, breadth 9 metres and height 9 metres. “It was intended to support Urja break through safely, by avoiding loss of soil inside. When the TBM breaks through, it carries soil with it,” he explained.
The rings being made in a circular fashion make the particles fall to the ground. “They could, in future, create a cavity and this could result in sinking of the buildings above. To avoid such a situation in future, we created this block,” he said.
There were many spots along the route the machine was tunnelling from Cantonment to Shivajinagar, where buildings are just five metres above the drilling level, the official added. These precautionary measures were taken after lessons learned from Metro Phase-I when sinkholes at a few places delayed the underground corridor by over a year.
All hurdles cleared for airport line
BMRCL Managing Director Anjum Parwez on Wednesday said the High Court had on Tuesday (September 21) given the agency permission to transplant trees for Metro Phase-II work. Speaking during an event to mark the breakthrough of Tunnel Boring Machine Urja, he said that Jakkur Flying School had given it a fresh No Objection Certificate (NOC) to go ahead with construction work for the KR Puram-Kempegowda International Airport Line, which would be in place by December 2024.
General Manager of BMRCL’s Social and Environmental Management Unit, Divya Shivram told TNIE, “We are unable to complete Metro stations at UM Kaaval, Jyotipura and Kothanur depot as we are awaiting permission to translocate around 900 trees. BMRCL will be planting 9,000 trees at Jayaprakash Narayan National Youth Centre, and other BDA and KIADB lands. We aim to start planting before removing or felling trees.”
CM Basavaraj Bommai reiterated that he had advanced the completion of Metro Phase-II to 2024. “I am closely monitoring the work and want the project to be completed by the deadline,” he said. He had advanced the deadline during the launch of the Mysuru Road-Kengeri Line on August 29 this year. Jakkur-based Government Flying Training School gave a fresh NOC a fortnight ago, said Hega Reddy, Executive Director, Civil-1, BMRCL.