Bengaluru: During construction of Phase-I, the Bangalore Metro Rail Corporation Limited (BMRCL) struggled to tunnel the 9-km underground stretch. Back then, it deployed six tunnel boring machines (TBMs) and the average time taken for tunnelling one kilometre was about seven months.
The underground section remained a bottleneck all through, rendering the metro corridor in South Bengaluru unusable although it was ready for three and half years. The BMRCL blamed complex geology and dense population for the delay .
Learning from this experience, the BMRCL plans to double the number of TBMs in Namma Metro Phase-II.The 13.79-km underground line, which is part of the 21.25-km Gottigere-Nagawara corridor, is a crucial segment that connects the South, Central and North Bengaluru, and continues further to link the Kempegowda international airport.This section will meet the east-west corridor at the MG Road interchanging station.
“Civil work on the underground stretch will be divided into four packages. As many as 12 tunnel boring machines will be put to use. The idea is to complete tunnelling in less than two years,“ BMRCL managing director Pradeep Singh Kharola said. Civil bids for the underground line will be floated aft e r t h e E uropean Investment Bank (EIB) approves funding, he added.
The 13.79-km underground line includes tunnelling double the length.In reality , each of the twelve TBMs will have to tunnel a distance of a little more than two kilometres.
“Using 12 TBMs is a good decision,“ Sanjeev V Dyamannavar, founding member of Praja RAAG, an advocacy group, said. “The fact that the tender for civil work is not yet floated is an indication that the metro work on this corridor will not start till 2018end. This is in spite of the Government of India approving the project way back in 2014,“ he added.
Land acquisition is another major challenge for BMRCL. The corporation has identified 50 hectares of land for acquisition. The Karnataka Industrial Area Development Board said it would take at least a year to acquire the land.