This is with reference to a news report titled “ 50 Metro stations at high risk: UN Study” which appeared in some newspapers on 25th June, 2013 and 26th June, 2013.
In this connection , we would like to point out that the Delhi Metro Rail structures are completely safe in case of any seismic or tectonic activities like earthquakes taking place in Delhi as the Metro Rail structures have all been designed to handle seismic events corresponding to zone 4 and all Indian codes IRC:6, BIS:1893, BIS:13920 and RIS codes which give guidance on designing of structures for earthquakes have been strictly followed in all the structural construction of the Delhi Metro Project .
These news reports have been quoting the United Nations study saying that the Metro Line is exposed to high flood and earthquake risk but the same United Nation study in its conclusion to these comments (Box 8.6) have clearly said that the direct risk to Metro structures and rail line structures have already been addressed and reduced owing to application of risk sensitive building codes.
Thus, the Metro design engineers have adequately addressed all risks to Metro structures which may happen during an earthquake. The Metro structures are, thus, absolutely safe for carrying passenger traffic and to avoid apprehension in the public mind about the safety of Metro structures we would also like to point out the following:
1) The most vulnerable part of structure for seismic event is the foundation due to liquefaction. To avoid this, deep foundations have been provided in zone susceptible to liquefaction. Every location of DMRC foundation has been assessed for liquefaction based on soil parameters and foundations have been appropriately chosen.
2) Other area of vital importance for seismic design is ductility detailing of reinforcement for which the guidelines as per relevant BIS code are being followed.
3) DMRC underground stations have also been designed for earthquake following the state of the art seismic guidelines evolved internationally.
4) Design for seismic events starts with dimensioning of structural members and selection of foundation type. Seismic forces are then evaluated as per guidelines provided in the relevant codes.
5) All Metro structures near the Yamuna Bank have been constructed with the approval of the Yamuna standing committee with simulation studies conducted by the Central Water and Power Research Station, Pune to ensure complete safety. Detailed hydrological studies were conducted and protective guide bunds have been constructed by the DMRC to address these issues.
In view of the above clarifications it is again reiterated that all Metro structures have been designed to ensure complete safety.