Bangalore Metro’s TBM Tunga Records Breakthrough at K.G. Halli

Tunnel Boring Machine S-839B operated by ITD Cementation India on Wednesday recorded a breakthrough at Kadugondanahalli (K.G. Halli) Station of the 21.386 km Bangalore Metro Pink Line (Reach 6) project.

Nicknamed Tunga, this was TBM S-839B’s 3rd of 4 planned breakthroughs and ITD Cem’s 5th of 8 breakthroughs planned for the 73.92 km Bangalore Metro Phase 2 project’s 4.591 km Package RT-04 (Tannery Road – North Ramp).

This Herrenknecht mixed-shield EPB machine was originally launched in June 2021. For its latest assignment, it built a 1184m tunnel from Venkateshpura to KG Halli boring at an average rate of 2.95m/day through mixed face hard rock conditions.

Here’s a summary of all completed drives:

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.

Video (check it out for some cool visuals from all station sites in RT-04)

Per BMRCL’s recent newsletter, as of October 31 TBM Bhadra (S-840B) working on the parallel southbound tunnel had completed tunneling 63.89% of 1186m after being relaunched in February 2023. Assuming it follows a similar tunneling excavation rate, I see it arriving at K.G. Halli sometime in late March 2024.

With this development, Tunga will now be dragged across Kadugondanahalli Station’s box and be relaunched for its fourth and final drive of roughly 935m towards Nagawara Station.

Overall tunneling progress for Phase 2 stands at 18.83 / 20.9 km with 23/26 tunnel breakthroughs recorded so far: 8/8 on Package RT-01 by Afcons, 4/4 on RT-02 by L&T, 6/6 on RT-03 by L&T, and 5/8 on RT-04 by ITD Cementation.

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– TMRG