BENGALURU: Namma Metro’s second Tunnel Boring Machine (TBM) will be taken out of service on Friday afternoon. ‘Avni’ will complete tunnelling the distance of 1,100 metre from South of MG Road Metro station up to Vellara Junction and will break through after 231 days. This being the second leg of its tunnelling journey, Avni’s tryst with Bangalore Metro Rail Corporation Limited (BMRCL) will come to an end.
This will be second TBM of BMRCL’s Phase-II to hang up its boots with TBM Varada completing its job on September 9 this year. Nine TBMs have been entrusted with the job of building an 13.8-km underground corridor for the Nagawara-Kalena Agrahara Line.
A senior Metro official told TNIE, “Avni will have its breakthrough at Rashtriya Military School at Vellara Junction. It is unique in two important aspects. Out of the nine TBMs hired for BMRCL, it will cover the maximum distance in terms of tunnelling. On January 6 this year, it had completed 487 days of tunnelling from Shivaji Nagar Metro station to MG Road station, a 1,086-metre stretch. It is also the first TBM that drilled below an operational Metro line when it tunnelled under Cauvery Emporium on MG Road on March 9 during its second leg, thereby crossing the Metro alignment of the Purple Line (Baiyappanahalli to Kengeri).”
In Phase-2, there will only be one more instance when such a crossing takes place, when Lavi, the TBM drilling parallel to Avni, crosses below the same stretch. Even as six other TBMs continue inching their way forward, work on kickstarting Rudra, which has ground to a halt three months ago due to garbage heaps blocking its tunnelling has begun.
“To deal with the garbage which has now almost become like manure, we will first drill a steel casing running to a diameter of 1.2 metre. The soil would be removed through it. A concrete structure will be laid above it.” It will take another four months for the procedure to be completed and ‘Rudra’ to restart its job. Elaborating on the unique challenges faced underground, the official said that TBM Varnika (Diary Circle to Lakkasandra) was drilling just 9 metre away from Rudra, but was going about its job smoothly.