BENGALURU: A crucial part of the first indigenously assembled tunnel boring machine (TBM) of Bengaluru Metro was lowered 60 feet below the ground at Vellara Junction on Thursday night. This kickstarts the tunnelling process from Vellara towards Langford Junction, which forms part of the underground corridor of the Red Line of Phase-II. What makes it unique is that the parts manufactured in Germany were imported, assembled in Chennai and transported via road to Bengaluru.
“This is the first indigenously-readied TBM for Bengaluru Metro. We have imported six TBMs from China for Metro Phase-II and three are to be readied at Chennai. This TBM is the first, while the other two are now clearing the Factory Assessment Test,” said a BMRCL source. The lowering of the ‘middle’ section of the TBM began at 9pm and continued very gradually for 30 minutes, the source said. The ‘cutter head’ and ‘tail’ will be lowered in the coming week, and the three parts will be assembled below ground.
The whole process was facilitated by a special Gantry crane, the first-of-its-kind to be used by BMRCL. “With the TBM weighing 130 tonnes, we needed something that can handle such a heavy load. This crane weighs 700 tonnes and can carry it comfortably,” he said. The crane will remain at the spot till tunnelling work is complete, as it needs to lift the TBM back to the ground,” he said. After drilling 700 metres, it will reach Langford, and begin tunnelling in the reverse direction, the source added.
The 13.92-km underground network between Nagawara and Dairy Circle Kalena Agrahara (formerly Gottigere) is part of the 21-km Red Line between Nagawara and Kalena Agrahara. The UG corridor is divided into four packages, where boring machines have completed various levels of drilling — TBM Avni is drilling from Shivajinagar to MG Road and has completed 270 metres, TBM Lavi is yet to start in the same direction, in the Cantonment to Shivajinagar package, Urja has completed 260 metres in the onward direction, while TBM Vindhya, which began in the same direction, has completed 100 metres. The stretch between Tannery Road and Nagawara hasn’t started as the TBMs are yet to arrive from Chennai. BMRCL MD Ajay Seth said the deadline for completion of the Underground Corridor is December 2024.