It is not just the bearings of the elevated portion of the Airport Metro Express Line that are troubling the Delhi Metro,another study points to problems with tunnels,that have led to the buildings above developing cracks.
After residents of Shahbad Mohammadpur,a residential colony in the vicinity of the tunnel connecting Aerocity and IGI Airport Metro stations,complained of tremors and cracks in their houses,Delhi Metro had commissioned Central Road Research Institute (CRRI) to conduct a study.
The report submitted to Delhi Metro last week observed that of the 50 observation points,only 10 per cent locations have average value of vibration around 82.5 Vdb.
The higher values of vibration observed in around 15 per cent of the structures could be due to a variety of factors like crossing of two Metro trains at the point of measurement,resonance of the building elements at the particular site, the study says.
The report states that comparing the measured vibration values with the available norms (highest range of commuter rail is 85Vdb and mass rapid transit at 15 metres is 80Vdb),the present scenario is not alarming as majority (85 per cent) of the structures are within safe limits.
The report suggests that running the trains at a speed around 75 kmph would provide relief to the residents,but this is contrary to the idea of a high-speed link.
The study has also recommended that the crossing of Metro trains near the problem areas should be avoided in order to ease the impact of vibration. Officials said this would mean running single-line operations or controlled movement of trains,bringing down the speed.
Other measures suggested are lubrication and roughness control of wheel and rail,and use of 60 mm rail pad near Shahbad Mohammadpur village and Baba Kharak Singh Marg.
Officials said during the period of suspension of operations,checks will be carried out in tunnels and rectifications made wherever possible.