Helen, one of the two tunnel boring machines (TBMs) deployed on Namma Metro’s East-West underground corridor, achieved a breakthrough when it emerged at the Vidhana Soudha underground metro station site at five minutes before noon on Wednesday.
Its counterpart, Margarita, is about 255 m away from the Vidhana Soudha station, according to a Bangalore Metro Rail Corporation Ltd, (BMRCL) spokesperson. Helen had commenced burrowing work from the Sir M. Visvesvaraya (Central College) underground metro station site on May 14 year and took about six months to dig the 725-m tunnel.
A BMRCL release said throughout the length, Helen encountered very hard rock of 300 mega pascal (MPA) with very short stretch of sand silt.
The breakthrough was accurate, the release said.
Minister for Urban Development, Law and Parliamentary Affairs S. Suresh Kumar witnessed Helen’s breakthrough, according to BMRCL Managing Director N. Sivasailam.
Long journey
It took almost one-and-a-half years for Helen to burrow about 1.7 km tunnel, starting from Majestic, from where it had commenced work in May 2011 to reach Vidhana Soudha. The TBM reached Central College station premises in March this year after burrowing 975 m of tunnel. Dismantling and reassembling of the TBM took about two months before it commenced its onward journey towards Vidhana Soudha.
Ambedkar statue
The delay in shifting of Dr. B.R. Ambedkar’s statue, which is located very close to the TBM shaft towards Cubbon Park (Minsk Square) underground metro station, could slow down further movement of the tunnel boring machines, BMRCL officials fear.
The Karnataka High Court had on December 12 directed the government to shift the statue within 15 days.
However, the government is yet to take any action with one more day remaining to comply with the court directive.
The machines have to be dismantled after their entry into Vidhana Soudha station premises and reassembled towards Cubbon Park station to burrow a distance of another about 500 m. The tunnelling work is likely to commence in February and end by May-June. A single TBM has already burrowed one tunnel between Cubbon Park station and BRV Parade Grounds and burrowing of the second tunnel on this stretch is under way. BMRCL is hopeful of completing the entire tunnelling work on the East-West corridor by June 2013.
