Delhi Metro vibrations, noise shake up residents; experts roped in
DMRC is preparing guidelines to mitigate noise levels at its elevated stations and testing a new technology to reduce vibration at its underground ones.Updated: Oct 05, 2019, 06:18 IST
The ever-expanding Delhi Metro Rail Corporation (DMRC) has been plagued with a new problem —complaints regarding vibrations and noise caused due to its train movements.
To address the problem, the corporation is preparing guidelines to mitigate noise levels at its elevated stations and testing a new technology to reduce vibration at its underground ones.
The DMRC has roped in the Central Road Research Institute (CSIR-CRRI) to prepare guidelines for measures to be taken along elevated corridors to ensure noise levels are within permissible limits.
Anuj Dayal, executive director corporate communications at DMRC, said, “We have received complaints from various places regarding noise along our elevated corridors. We had asked CRRI to prepare guidelines about three months ago, as there is are no such guidelines available worldwide, specifically for Metro systems. Wherever there is a need, we are retrofitting the tracks to minimise noise and vibration levels.”
The guidelines will provide parameters for installing noise barriers depending on noise level, location of the station and distance of the buildings in the vicinity. There are 181 elevated stations in Delhi, with the Metro cutting through residential areas such as Karol Bagh, East of Kailash and Mayur Vihar.
According to Dr Nasim Akhtar, principal scientist at transportation planning and environment division, CSIR-CRRI, “We will recommend the use of frequency-based noise barrier to be installed at elevated tracks so that there is no noise related issue in areas around the stations or along the tracks.”
Akhtar, who is working on the guidelines, carried out a survey on Metro tracks in Dwarka recently, to record the exact noise level on the tracks. “The noise level is close to 80 dB(A) on the tracks. In the guidelines, we will recommend height and type of the noise barrier depending on the distance of the nearest buildings from the station or tracks, height of nearby structures and elevation of the tracks, among other factors,” said Akhtar.
He said that the guidelines will be submitted to DMRC by the end of this month.
The vibration issue
With 68 underground stations, mostly in south and central Delhi, DMRC has been receiving several complaints regarding vibrations.
Residents of Saket, Hauz Khas, Begumpur, Shahbad Mohammadpur, Sarvpriya Vihar have complained that they feel the vibration every time a train passes in the tunnel.
With four Metro corridors — Yellow line (HUDA city centre-Samaypur Badli), Blue Line (Dwarka sector 21-Noida city Centre), Violet line (Kashmere Gate-Raja Nahar Singh) and Airport express line — passing through central Delhi, residents of Luytens’ Delhi too have complained about vibrations and rumbling noises inside their bungalows.
Earlier this year, BJP leader and former MP, Murli Manohar Joshi, had complained to DMRC in this regard. “We could hear the sound of trains passing underneath the house. DMRC, however, was prompt to address the issue. Though the problem is still there, it has reduced substantially,” said Rajiv Belwal, personal secretary to Joshi.
DMRC has started a trial to test a new technology on a 300 metre long stretch at Central Secretariat to reduce vibration at source.
DMRC has installed a new fastening system (Vanguard), which holds the tracks from either side due to which they don’t touch the surface. “This results in considerabe reduction in vibration at source. We are testing this system for the last two months. We will have to study it for a longer duration to assess it longterm impact. This system has been used in the Tube in London,” said Dayal.
Vibration is caused due to the interaction between the wheel and the rail track in underground stations. As per DMRC, vibration on underground tracks is between 70-80 VdB.
“Vibration or rumbling sound is often experienced in the structures above the ground depending on factors such as the type of underground surface (rocky or soil), proximity of structures to the tunnel etc. World over, thick pads are provided underneath the tracks or floating chambers are constructed to address the problem of vibration,” said Akhtar.
DMRC officials say that in all its tracks constructed in Phase-I and II, there were two layers of thick padding provided on the tracks to reduce vibration. But in Phase-III, the Metro added another layer of padding and used the mass spring system technology. In this, a thick polyurethane pad sheet is spread underneath the tracks.
“In Phase III, we have extensively provided mass spring system to reduce vibration levels. We have used this where the residential buildings were too close or we suspected that it could lead to vibration-related problems. We regularly do the rail grinding and wheel profiling to ensure the surface is smooth,” said Dayal.