Delhi Metro Rail Corporation (DMRC) is going to monitor vibration levels caused by train movement at 80 locations along Yellow (Samaypur Badli-Huda City Centre) and Violet (Kashmere Gate-Ballabhgarh) lines.
The locations are expected to be mainly in central and south Delhi, apart from Gurgaon and Faridabad. DMRC has floated a tender to engage an agency to carry out the task, including 24-hour monitoring at 60 locations and eight-hour monitoring at 20 places. The agency would collect samples from these 80 locations and the exercise has to be completed within a year.
A DMRC spokesperson said that similar exercises were being carried out for a decade now. The tender has been floated as part of routine monitoring work being carried out since 2011. “This practice is primarily adopted to eliminate vibration-related problems at locations where residential buildings are too close or places where it is anticipated that it may lead to problems,” he added.
“In the past, monitoring was carried out at Saket, Malaviya Nagar, Begumpur, Hauz Khas, Khan Market, Golf Links, Azadpur, Dashrathpuri, etc. The objective is to randomly collect samples from different locations to assess whether the vibration levels are within acceptable limits. If any variation is reported, then necessary steps are taken to mitigate them,” said the spokesperson, adding that the actual number of locations could vary based on conditions on the ground and technical requirements.
The teams that would carry out the monitoring would be headed by a technical analyst with at least three years’ experience in analysing such data and preparation of the report, apart from site supervisors with experience in carrying out the task and knowledge of operating equipment, including transfer of data, etc.
The experts would use “tri-axial velocity sensors” for the exercise, apart from transit vibration monitoring instruments with analysing software. At each location, vibrations would be measured at a sampling rate of minimum 1,024 samples per second in a frequency range of 1 to 300Hz. Recording time for each sample would be a minimum of 30 seconds.
The monitoring equipment would have a minimum memory capacity of 1GB to store at least 2,000 events of 30 seconds each. The spokesperson said other reasons for carrying out such an exercise included routine track-level vibration monitoring, which is done twice — before taking up maintenance activities of tracks and rolling stock and on completion of those activities.
“This type of monitoring helps in ensuring that track and rolling stock systems are performing within the defined parameters,” he added. “The monitoring is conducted based on noise and vibration guidelines of Research Designs and Standards Organisation and Federal Transit Administration.
Since the start, DMRC has taken adequate care to ensure that vibration levels in its underground sections remain within permissible limits,” said the official. The official added, “The practice prevalent currently includes providing two layers of thick padding on the tracks to reduce vibration in Phase-I and II projects. Strengthening was done with one more layer in Phase-III with the use of mass spring system technology in which a thick polyurethane pad sheet was spread underneath the tracks.