BENGALURU: Bengaluru Metro's tunnel boring machine (TBM), 'Urja', which was tunnelling on its second drive from Cantonment to Pottery Town is all set to have its breakthrough on Thursday around 10 am. It has taken 190 days to complete tunnelling the stretch of 907 meters.
Urja began its journey on December 21, 2021. Prior to that, it had tunnelled between Cantonment and Shivaji Nagar stations for 855 metres and emerged on September 22 last year. The Chinese-made machine is boring underground along with 8 other TBMs to build a 13.8-km underground corridor for the Nagawara-Kalena Agrahara Line of Phase-II.
Larsen & Turbo is carrying out the tunnelling work here for Bangalore Metro Rail Corporation Limited (BMRCL).
Asked about the challenges encountered, a senior official said, "Tunnelling beneath the railway line near Cantonment was our biggest challenge. We had to ensure there was no safety issue involved for rail passengers. Again, we had to be careful when tunnelling beneath the buildings along the stretch."
After Urja, which weighs around 600 tonnes, completes its journey on the South end of Pottery Town, it would be dragged to the North end. "Many power jacks would be deployed for this opreation. The shield portion (Cutter Head) would be pushed first and the gantries would be pulled next," he said.
The process could take nearly five months. Later, the TBM would be taken out of a vertical shaft already erected near Shaadi Mahal slowly which could take another month. Urja's work for BMRCL would therefore end completely within six months, he added.
The vertical shaft will also be used for exit purposes by two other TBMs tunnelling in this direction from Venkateshpura.