BENGALURU: To reduce the impact of vibrations of trains running on underground tracks on buildings and structures in its vicinity, the Bangalore Metro Rail Corporation Limited (BMRCL) plans to install a special safety system on the tracks. This is being planned on 9 km out of the 13.8 km Underground Corridor from Dairy Circle to Nagawara of Phase-2’s Pink Line. Director, Projects and Planning, BMRCL, D Radhakrishna Reddy told TNIE,
“To attenuate the vibrations, we are going to adopt a Mass Spring System on the underground tracks of the Reach-6 line from Nagawara to Kalena Agrahara. This follows a study conducted by BMRCL to assess the travel of vibrations and their likely impact on structures.”
Twin tunnels are being built at a depth of eight to nine metres below ground level. “The tracks are laid at the end of the tunnel and so this is at a depth of 13 metres of 14 metres below the ground. Though this is a considerable depth below the ground, vibrations due to dynamic loads coming into play due to the contact of rail and wheel may travel to the buildings above,” Reddy explained.
The study revealed that only 9 km of tracks need to be provided with vibration mitigation measures. “In the Mass Spring System, a special pad of specific elastic characteristics made of Polyurethane material is provided below and on the sides of the track slab.
This will completely isolate the track system from the tunnel so that vibrations from the trains are damped significantly before getting transmitted to the tunnel and in turn to the soil strata and to the buildings,” the Director explained.
The intensity of the vibrations will depend on the characteristics of the Metro track support system, soil strata above the tunnel and the type and condition of the buildings, he added. “The Mass Spring System will be put in place before the tracks are laid,” the official said.