New Record for Bangalore Metro: ITD’s TBM Tunga Bores 308m in July

ITD Cementation India’s tunnel boring machine Tunga (S-839B) has set a new local record for Bangalore Metro while working on the 21.386 km Bangalore Metro Pink Line (Reach 6) project.

This Herrenknecht mixed-shield EPB machine is currently on its fourth and final tunneling assignment on 4.591 km Package RT-04 (Tannery Road – North Ramp) of the 73.92 km Bangalore Metro Phase 2 project.

With 3 breakthroughs already recorded, TBM Tunga had started its final drive of 938 meters on February 1, 2024 from Kadugondanahalli Station towards Nagawara Station’s south TBM retrieval shaft. By the end of June, it had bored 469 meters (built 335 rings) before two major sinkholes opened up on the surface-level and had to be backfilled with grout.

After passing through that zone, Tunga in the last month bored an impressive 308 meters thanks to favorable soil conditions as suggested by the geotechnical investigation report. The previous monthly best in Bangalore was 273 meters recorded by Larsen & Toubro’s CRCHI TBM Urja on 2.884 km Package RT-03 (Shivajinagar – Cantonment – Pottery Town – Shadi Mahal Shaft)

Tunga on Wednesday night came to a temporary halt for a regular cutterhead inspection (CHI). As of the night of July 30 (Tuesday), here’s how things stood for ITD’s machines:

• TBM Tunga: 776/938m (548/670 rings)
• TBM Bhadra: 416/941m (290/672 rings)

ITD Cem’s scope of work involves building a combined total of 6.34 km twin tunnels, roughly 360 meter ramp at Nagawara, and four stations at Tannery Road, Venkateshpura, Kadugundanahalli (formerly Arabic College) and Nagawara.

Here’s a summary of Tunga’s drives:

• Venkateshpura to Tannery Road (822m): June 2021 – June 2022
• Tannery Road to Shadi Mahal TBM Retrieval Shaft (209m): June 2022 – August 2022
• Venkateshpura to Kadugondanahalli (1184m): October 2022 – December 2023
• Kadugondanahalli to Nagawara (938m): February 2024 – August 2024 (likely)

I hear ITD Cementation is currently targeting to host Tunga’s breakthrough event around August 20 and Bhadra’s breakthrough event – the final of 26 breakthroughs for Phase 2 project – around September 20.

That of course depends on how things progress in the coming weeks, and the availability of state ministers who’d want to be present for the final event. I’ve covered 100+ TBM breakthroughs on my site and have heard several times of machines across India purposely being halted for days just because a minister couldn’t make it to the originally scheduled event.

Anyhow – following the final breakthrough, ITD Cem’s pending civil work will largely include cross-passage works, station completion (excluding finishing) and cut & cover ramp works. Systems installation work for track, signaling, traction etc. by different contractors (see list) within the tunnels will happen in parallel and progress as ITD Cem hands them over.

Like other metro lines, Bangalore’s Pink Line will open in stages and at this time I expect commercial operations at Nagawara Station to start no sooner than Q3 2026. The start of operations on the elevated section of the line – which I envision would happen no sooner than Q1 2026 – largely depends on the delivery of trains. The 1st prototype BEML train from Package 5RS-DM is expected to arrive around June 2025.

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– TMRG