TBM Tunga sets new records by creating 308m tunnel for Bangalore Metro Phase 2

Bangalore, India (Metro Rail Today): ITD Cementation India’s tunnel boring machine (TBM) Tunga S-839B) has set a new record for Bangalore Metro by boring 308 meters in July. This achievement is part of the 21.386 km Bangalore Metro Pink Line project.

The Herrenknecht mixed-shield EPB machine Tunga is working on its fourth and final tunneling assignment for Package RT-04, which covers 4.591 km from Tannery Road to the North Ramp. Tunga began this final 938-meter drive on February 1, 2024, from Kadugondanahalli Station towards Nagawara Station’s south TBM retrieval shaft.

By the end of June, Tunga had bored 469 meters and constructed 335 rings before encountering two major sinkholes at the surface, which required grouting. After overcoming these challenges, Tunga achieved an impressive 308 meters of tunneling in July, aided by favorable soil conditions. The previous monthly record in Bangalore was 273 meters, set by Larsen & Toubro’s CRCHI TBM Urja.

As of July 30, TBM Tunga had completed 776 meters of its 938-meter drive and built 548 rings. TBM Bhadra, another machine on the project, had bored 416 meters out of 941 meters and built 290 rings. Tunga recently halted for a regular cutter head inspection.

ITD Cementation’s scope includes constructing 6.34 km of twin tunnels, a 360-meter ramp at Nagawara, and four stations: Tannery Road, Venkateshpura, Kadugundanahalli, and Nagawara. The TBM’s drives are summarized as follows:

• 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 (expected)

ITD Cementation plans to hold Tunga’s breakthrough event around August 20 and Bhadra’s breakthrough event, the final of 26 breakthroughs for Phase 2, around September 20. The schedule for these events may be adjusted based on progress and the availability of state ministers.

After the final breakthrough, the remaining work includes cross-passage construction, station completion (excluding finishing), and cut-and-cover ramp works. Systems installation for track, signaling, and traction will occur concurrently. The Bangalore Pink Line will open in stages, with commercial operations at Nagawara Station expected no earlier than Q3 2026. The elevated section of the line might start operations no sooner than Q1 2026, depending on the delivery of trains, with the first prototype expected around June 2025.