Eighteen piers in three different under-construction Metro corridors have been detected with cracks. While the Delhi Metro Rail Corporation (DMRC) maintained that the cracks were minor,it is unwilling to take any chances and has directed an expert team from Shirish Patel and Associates to re-check the design of all 18 points.
During inspection,Delhi Metro engineers have found hairline cracks on eight piers of the Central Secretariat-Gurgaon corridor,two piers on the Noida corridor,and eight on the Central Secretariat-Badarpur corridor, DMRC spokesperson Anuj Dayal said.
The expert team that was engaged after the Zamrudpur incident to conduct a structural audit of all cantilever piers of Phase-II has now been directed to re-check designs on these piers.
Dayal said,The cracks appear to be minor but they are being kept under observation by Metro engineers. Surface cracks are not uncommon and Indian standard codes for design of reinforced concrete structures permits tension cracks within limits.
Some of the piers detected with cracks have been supported with metal struts. Pier number 192 and 193 on Central Secretariat-Gurgaon line,and piers 10 and 14 on the Noida corridor saw metal struts being put up in the last two days after the cracks were spotted.
DMRC chief E Sreedharan had inspected the cracks on the Noida corridor on Sunday.
Officials at Gammon India Limited,contractor for the Badarpur and Noida lines on which cracks have been found,said these were old surface cracks and that DMRC was informed about them earlier.
For now,DMRC is awaiting the final report from the consultants. Officials said corrective action will be taken once the locations are examined. While pier 67 and a couple of adjoining piers at Zamrudpur,where the recent accident occurred,will be demolished,a decision on other piers will be taken after details of design and nature of cracks are studied,DMRC officials said.
But if the piers are found with design faults and need extensive work,it might delay commissioning of the lines,DMRC officials said. Trial runs on the Noida corridor began on Saturday and the line is slated to be opened in a months time. The Gurgaon corridor is scheduled to open in January 2010,and Badarpur in late 2010.
For now,Dayal said,Ultrasonic testing and rebound hammer testing will be done first to check integrity and quality of the concrete. In addition,DMRC will also conduct load testing wherever considered necessary.
But there is no reason to panic as similar testing was done during Phase-I of the construction as a precautionary measure whenever required.
Noida corridor: Gammon India
Central Secretariat-Badarpur: Contractor Gammon India
Central Secretariat-Gurgaon (elevated section from Qutab Minar-Gurgaon is elevated and has cantilever structures): ITD CEM JV
(Note: contractors engaged only on sections where cracks have been found,not on entire corridor)
* 100 years: estimated life of a pier
* DMRC has a maintenance wing that undertakes checks for structural and operational systems on regular basis but DMRC officials maintain cracks were never noticed earlier