NOIDA, India, March 24, 2015 /PRNewswire/ --
The vibrations felt by residents in areas near or above metro lines/tunnels have always been a matter of concern and with numerous media reports in the recent past covering this pressing issue, it is important that we gain a perspective into this problem and understand how vibration isolation technology can prevent and mitigate this phenomenon.
(Photo: http://photos.prnewswire.com/prnh/20150324/10118891-a )
(Photo: http://photos.prnewswire.com/prnh/20150324/10118891-b )
Complaints from residents of buildings overlying the metro tunnel have been highlighted very well by a few media reports as under:
"The court has now sought a reply from the Centre on the allegation levelled by the residents of D-Block, Saket, that they are unhappy over the high levels of noise and vibration caused by the movement of the Delhi Metro Rail Corporation-run trains running on the Yellow Line connecting Jahangirpuri with HUDA City in Gurgaon". http://urbanupdate.in/governance/delhi-residents-seek-hc-intervention-metro-disruption
"My house shakes when the metro passes underground. What measures should I take?"- http://www.quora.com/My-house-shakes-when-the-metro-passes-underground-What-measures-should-I-take
"The residents of the Shahbad Mohammadpur, which is a residential colony, in the vicinity of the tunnel connecting Aerocity and IGI Airport Metro stations have complained of cracks and tremors in their houses."-
http://asiabizz.com/13892/airport-metro-residents-complain-of-cracks-and-vibrations/
It is clear that buildings overlying or close to the metro track are prone to be affected by ground-borne-noise and vibration. Vibrations can be felt by people staying in buildings less than 10 meter distance from the line axis and in addition, structure borne noise can also cause disturbance.
Vibration propagation path is demonstrated in Figure 1. Typical vibration level at buildings above tunnel may reach more than 90 VdB easily as demonstrated in Figure 2.
Resulting vibration level of 90VdB inside the building is about 8 times more than the threshold value of human annoyance of 72 VdB** as can be calculated from the following formula: 20LogT = 90VdB - 72VdB; 20LogT =18VdB ; LogT = 18/20=0.9 ; T = 10 ^ 0.9 = about 8.
**According to ISO 2631-2, the limiting RMS velocity is 0,0001m/s = 0,1mm/s for the residential buildings. The corresponding vibration level in VdB = 20*LOG (v / vref) = 20*LOG(0,1 / 0,0000254) = 72dBv. This is the threshold value of human annoyance and also corresponds to FTA-USA as adopted worldwide.
Appropriate measures are needed to attenuate the vibration levels by 20VdB (minimum), especially for the buildings overlying the tunnel. The best way to achieve this attenuation of resulting vibrations levels is through installing a Mass Spring System (MSS) which consists of a floating track-bed and have been adopted by many metro operators around the world. An MSS, as its name suggests, comprises of a mass, i.e., the concrete track-bed and a spring which could actually be a steel spring or an elastomeric pad supporting the concrete track-bed in a discrete manner.
The functioning of the mass spring system can be understood from the points below:
About GERB
GERB has been a forerunner in providing MSS solutions to urban mass rapid transit sector around the world. GERB MSS has been installed under more than 300 km of metro tracks in countries like Germany, France, Switzerland, UK, USA, China, Brazil, Russia etc. For more information, log on to www.gerb.in.
Primary Media Contact
Snigdha Dwivedi
[email protected]
+91-9560444968
Media Consultant
GERB Vibrations Control Systems Pvt. Ltd.
Secondary Media Contact
SK Mishra
[email protected]
+91-9717822331
Project Manager
GERB Vibrations Control Systems Pvt. Ltd.
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