Tunnel Boring Machine Tunga (TBM) at the KG Halli metro station on Wednesday.
Credit: BMRCL
Bengaluru: Almost 90% of tunnelling on Bengaluru's longest underground metro line has been completed.
On Wednesday, Tunnel Boring Machine Tunga emerged at the KG Halli metro station after boring 1,184.4 metres from Venkateshpura. This was Tunga's second of three breakthroughs and the 21st out of 24 breakthroughs on the 21.26-km Pink Line, which will connect Kalena Agrahara to Nagavara via MG Road and Tannery Road.
Metro engineers and workers erupted in joy as Tunga broke ground on Wednesday morning, completing its 1,184.4-metre assignment between Venkateshpura and KG Halli in 401 days. It bored through rock, soil and a mixture of both.
The German-made Herrenknecht machine was first launched in the city on July 23, 2021, and took 13 months to tunnel 1,264 metres between Venkateshpura and Tannery Road.
Of the total 20,992 metres on the Pink Line, 18,832.30 metres have been tunnelled. This translates into 89.7%, Bangalore Metro Rail Corporation Limited (BMRCL) said in a statement.
The BMRCL deployed nine machines to bore through 20,992 metres on the Pink Line. Seven of these machines — Urja, Varada, Avni, Lavi, Vindhya, Vamika and Rudra — have finished their job.
With Tunga finishing its second drive, the BMRCL will drag it through and deploy it for the third drive (935 metres, from KG Halli to Nagavara).
"The drag-through could take up to 45 days, but we are trying to make it happen in about a month. The cutter head has to be welded before the TBM gets ready for the next assignment. We hope to start the third drive in mid-January," a well-placed source in the BMRCL said.
The last TBM, Bhadra, is currently creating the second tunnel from Venkateshpura to KG Halli. It has tunnelled about 850 metres of the total 1,186 metres. The BMRCL hopes it will break through by January-end and they will be able to deploy it for the third drive (939 metres from KG Halli to Nagavara) in March. The final drive will be completed by the end of 2024.
The Pink Line's deadline is March 2025.