RailEnquiry

While slurry-based tunnel boring machine is considered to be better for hassle-free operations as the muck generated during burrowing is transmitted through slurry in the pipeline, it may set off cavities on the ground above if the earth strata comprises loose soil.BMRCL officials had to fill such cavities with cement that had been triggered under K.G. Road during tunnelling between Majestic and Central College. All the cavities were filled, said Subrahmanya Gudge, Deputy Chief Engineer (Underground), BMRCL. However, these went unnoticed by people who must have thought it was some routine work related to Namma Metro. When the slurry is moved in high pressure during the course of tunnelling, the loose soil above may get settled causing cavity on the ground surface above. “We have installed settlement markers above the ground on the tunnel alignment. Every night the markers are inspected, and if the settlement is more than 3 mm deep, it is noticed the next morning. A hole is drilled on the settlement spot and cement is pumped in to fill the cavity,” he said.