Nearly three months after tunnel work was commissioned, the Tunnel Boring Machine (TBM) christened Urja has drilled a distance of 144 metres from Cantonment Station towards Shivajinagar. It was the first TBM to commence drilling work on July 30 under Phase II of the Namma Metro project.
However, tunnelling work was temporarily stopped by the appearance of a sinkhole last week.
The sinkhole has been grouted. Once it settles down, the TBM will resume work, said a Bangalore Metro Rail Corporation Limited (BMRCL) official.
BMRCL has estimated that to tunnel a distance of 850 metres, the machine would take nine months. Another 706 metres of excavation work is required to achieve a breakthrough at Shivajinagar. At the time of commissioning work, the BMRCL had maintained that the machine would drill through 250 metres of hard rock, 350 metres of mixed ground condition and about 225 metres of soil.
As per the plan, after Urja crossed over 100 metres of excavation, one more TBM named Vindhya started the journey from Cantonment side. As on October 17, the machine has tunnelled a distance of around 18 metres. Vindhya will dig a parallel tunnel towards Shivajinagar.
B.L. Yeshwanth Chavan, Chief PRO of BMRCL, said that a third machine, Avni, which started tunnelling from Shivajinagar to Rashtriya Military School has resumed work after facing hurdles due to a sinkhole in Shivajinagar metro station construction area.
The official said, The sinkhole problem has been fixed. The machine resumed work and proceeded to dig 11 metres. Once Avni crosses 100 metres, another machine, Lavi, will commence tunnel work from Shivajinagar.
Under Phase II of Namma Metro, the BMRCL is building a 13.9-km underground line from Jayanagar Fire Station to Nagawara. An interchange station at Nagawara will be linked with the ORR-airport line that connects Silk Board with Kempegowda International Airport (KIA). The alignment has 12 underground stations and 10.37-km of twin tunnels.
For the rest of the reaches (Dairy Circle to Rashtriya Military School and Tannery Road to Nagawara), the BMRCL is expecting arrival of news TBMs in four months.
BMRCL has acquired 95% of the land needed for the project, but is facing hurdles at Langford, Lakkasandra and Rashtriya Military School.