Tunnel Boring Machine Tunga during its final drive from KG Halli to Nagavara.
Credit: BMRCL
Bengaluru: In a remarkable achievement, Namma Metro's Tunnel Boring Machine (TBM) Tunga bored 308 metres in July, breaking the previous monthly record of 273 metres set by TBM Urja.
Tunga's feat was a "pleasant surprise", a BMRCL official said, especially since it was halted for four days due to a sinkhole on the road surface between KG Halli and Nagavara on June 27.
The German-made Herrenknecht EPB machine (S839B) tunnelled 9.93 metres per day on average in July. For comparison, most TBMs tunnel average just 3-5 metres per day.
Between February 1 and June 30, Tunga tunnelled only 469 metres, averaging 3.19 metres per day. Overall, it has tunnelled 777 metres since February 1 and has 161 metres remaining.
A senior official in Bangalore Metro Rail Corporation Limited (BMRCL) attributed Tunga's brisk progress to favourable terrain. "It was all soil. There was no rock or major breakdowns," the official told DH.
The BMRCL is now hopeful that Tunga will finish tunneling by the end of August, two months ahead of schedule.
Tunga's sister TBM, Bhadra, is also on its last assignment, boring the parallel tunnel. So far, it has tunneled 412 metres (294 rings) out a 939-metre target.
"Bhadra has encountered a bit of rock, so we are going slow. But since it's boring the parallel tunnel, we expect the same terrain ahead. We hope it will achieve a breakthrough by October," the official explained. The BMRCL's official estimate for Bhadra's breakthrough is November.
The 21.26-km Pink Line will connect Kalena Agrahara to Nagavara via Dairy Circle, MG Road and Shivajinagar.
It includes a 13.76-km underground section (Dairy Circle to Nagavara) and a 7.5-km elevated section (Dairy Circle to Kalena Agrahara).
The underground section consists of twin tunnels totalling 21.9 km. With Tunga and Bhadra boring in the Pink Line's final section, only 688 metres have to be tunnelled on the Pink Line.
Meanwhile, station work is progress well in the Pink Line's last package (Bengaluru Cantonment-Nagavara). Station work is 85-90% complete at Bengaluru Cantonment and Pottery Town and 75% complete at Tannery Road, Venkteshpura, KG Halli and Nagavara, the official said.
The station building of Nagavara, the Pink Line's northern terminal, has risen above the ground. "Concourse and track-level works have been completed. The rooms are getting ready. Track-laying works are also going on," the official noted.
Station work progress is 85% at Dairy Circle, Lakkasandra and Langford Town and 95% at Rashtriya Military School (Vellara Junction), MG Road and Shivajinagar, another official in the know said.
"We have commenced finishing works, which include block masonry, plastering, painting and flooring. Electrical, signalling works and installation of lifts and escalators will start shortly," the official stated.
According to the official, the pending work will take another year. "We are targeting a 2025-end deadline for opening the Pink Line," he said.
Bengaluru-based BEML will supply 96 coaches for the Pink Line and 126 coaches for the Blue Line. As per the schedule, BEML will start delivering coaches in June 2025 and complete the order by the end of 2026. On average, it would supply 2-3 coaches per month.