BENGALURU: Namma Metro’s Tunnel Boring Machine (TBM) `Lavi’ commenced its eight-month journey from MG Road to Vellara Junction on Friday. The machine, which has been repaired and re-launched in a record duration of one month, will drill a distance of 1,110 metres below the ground before it grinds to a halt. Lavi is one of the nine TBMs carrying out tunnelling work for constructing an underground corridor which runs a total distance of 20,945 metres for the Nagawara-Kalena Agrahara Line of Phase-II. It had earlier tunnelled a distance of 1,086 metres from Shivajiagar to MG Road and reached its destination on April 14.
Speaking to The New Indian Express, a senior Namma Metro official said the unique achievement became possible after all the repair works that had to be carried out in the China-made machine when it tunnelled during its earlier leg, were done while it was being shifted from one end of MG Road to the other. “In technical terms we call it `Drag Through’. The TBM was being readied even as it was dragged slowly underground on the 200-metre stretch of MG Road from its north-end (junction of Cubbon Road and Kamaraj Road) to its south-end (junction of Kamaraj Road and MG Road). Four hydraulic jacks were used to shift the 350-tonne machine,” the official said.
Work was in progress 24x7 during the period with 40 workers working in two shifts, he added. “A platform was erected near the Cutter Head that runs to a diameter of 6.5 metres. Parts like scraper, cutter disc, drag bit and housing (base of machine) had to be arranged. We had to replace all the 44 cutter discs on the head cutter before its new trip,” the official said. The other machines involved in underground operations are Rudra, Vamika, Varada, Avni, Urja, Vindhya, Tunga and Bhadra.