Tunnelling for Bengaluru Metro tougher than anywhere in the world, says official

 Given Bengaluru’s complex geology, tunnelling for Namma Metro’s east-west corridor, which fully opened on Saturday, was tougher than the similar underground projects in Delhi.

The deadline for the project was set based on the Delhi model but Bengaluru’s geology delayed opening of the underground section.

This is what contractors and officials of the Bangalore Metro Rail Corporation Limited (BMRCL) said at a media interaction on Wednesday, recalling the challenges they faced during tunnelling.

Chris Reeves, who headed the team that tunnelled 5.5 km with tunnel boring machines (TBM), said the excavation was more challenging than anywhere in the world. “Tunnelling through the huge boulders under important buildings like Central College and Vidhana Soudha was difficult even after using specialised and complex machinery,” he noted.

The task demanded operating the TBM in a controlled pressure at the excavation chamber depending on the soil conditions. “The work was much harder than what we expected but no life was put to risk in the process. The machines had inherent safety features,” he said and added that there were a couple of learning incidents for them. He said it was difficult to dig even 18 metres a day while the same contractors were able to tunnel 33.6 metres a day in Delhi.

Siddanagouda Hegaraddi, Chief Engineer, BMRCL, said they completed the work at the Majestic station in less than four months, as a result of proper interface with different agencies. The underground section linking Majestic with MG Road was ready three months ago, but the BMRCL wanted the intersection to be fully ready. For the Majestic station alone, more than one lakh cubic metres of concrete was used, which is enough to build a dam, he said.

No shortcuts

The BMRCL did not compromise with safety aspects even though there was criticism of the delay in work. “Sometimes, we were tempted to take shortcuts, but we did not do that considering the safety of passengers. It’s been almost five years since Metro opened for public and there have been no mishaps,” said Vijay Kumar Dhir, Director (Project and Planning), BMRCL.

Solar energy at Baiyappanahalli

N M Dhoke, Director (RSI), BMRCL, said a solar system would come up at the Baiyappanahalli Metro Depot in six months. The solar energy would be used for auxiliary requirements of the stations, not for the trains. “We will take up a similar project at the Peenya Metro Depot and in the second phase of Namma Metro,” he added.

The BMRCL is also considering increasing the frequency of Metro trains. “At present, each Metro train of three coaches has passenger capacity of 975. If the demand goes up, we will run a train every 3 minutes. We are also considering doubling the number of coaches if the passenger strength is high,” he said. Metro trains can run at a speed of 80 kmph, but because of proximity of stations and curves, the speed is reduced to about 34 kmph, he added.

CBD traffic down by 5%?

Former Additional Commissioner of Police, M A Saleem, tweeted on Wednesday that the fully inaugurated purple line of Namma Metro might have reduced traffic by 5% in the central business district.

BMRCL Spokesperson U A Vasanth Rao told Deccan Herald that number of passengers on east-west and north-south corridors exceeded 5 lakh in the last five days.