9 Tbms At It: 70% Of City’s Longest Tunnel Work Over | Bengaluru News – Times of India


BENGALURU: As the city’s central business district bustles with life, giant tunnel boring machines (TBMs) tirelessly cut through the rocks underneath to pave the path for Namma Metro trains.
The tunnels are being dug up by nine TBMs through the city’s commercial hub and densely populated areas on a 14km stretch between Dairy Circle and Nagawara, as part of Pink Line.

Bangalore Metro Rail Corporation Limited officials said the machines which are drilling 18m-21m below the surface, cutting through areas like MG Road and Shivajinagar for trains to crisscross, may see light by September 2023. However, commercial operations of the Pink Line will commence in December 2024. BMRCL records show around 70% of the tunnelling work has been completed. Of 21.2km work (twin tunnels), around 14.3km has been completed so far.
Statistics show 13 out of 24 breakthroughs on the section have been achieved so far. Once the tunnelling work is completed, BMRCL will take up other work on cross-passage (short tunnel that connects two parallel tunnels), track laying, signalling and telecom, traction power supply, station work etc.
The underground stations are: Dairy Circle, Lakkasandra (Mico Industries), Langford Town, Rashtriya Military School (Vellara Road), MG Road, Shivaji Nagar, Cantonment, Pottery Town, Tannery Road, Venkateshpura, Kadugundanahalli (Arabic College) and Nagawara.
TBM Rudra to resume work in 15 days
TBM Rudra, which was stuck after encountering a garbage pile-up near Lakkasandra will resume work in 15 days. TBM Rudra, which was drilling from Dairy Circle to Lakkasandra station (745m) since March 26 has completed only 50% (373.8) of the work. Officials said TBM Rudra will achieve a breakthrough by March 2023. “We have put up a concrete surface to resume its journey,” said an official.
The challenges
As compared to Phase 1, Phase 2 tunnelling is progressing with relatively fewer hurdles. When cutter tools of TBMs move from soft soil to hard rock in mixed- ground conditions, which is common in Bengaluru, it can often be tough. The challenges while negotiating mixed-face geology are over-excavation, excessive damage to cutter tools and regular cutter-head interventions (repair/maintenance). Others are presence of boulders, mainly granite and dolerite, formation of sinkholes during TBM excavation in mixed ground conditions, loose soil etc.

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