Metro Rail has discovered cracks in 16 more pillars, taking the total to 18 over the last two days; two pillars with cracks were reported on Sunday.
They will now be subjected to more stringent tests to ascertain the magnitude of the damage.
Delhi Metro Rail Corpo-ration’s own engineers found these cracks during inspections ordered in the aftermath of a pillar collapse near Zamrudpur in south Delhi on July 12, in which six people were killed.
“The cracks appear superficial by and large,” said Metro Rail spokesperson Anuj Dayal. “But the managing director (E. Sreedharan) has been over cautious after the July 12 accident and has ordered complete investigation of these piers.”
All the pillars with cracks were cantilevers — inverted L-shaped pillars — as was the one that collapsed in Zamrudpur.
Eight of these pillars (also called piers) were on the Central Secretariat-Badarpur line, of the Zamrudpur infamy, another eight on the Central Secretariat-Gurgaon line and the remaining two on the Yamuna Bank-Noida stretch.
Two of these lines are being constructed by Gammon India, a Rs 3,657 crore engineering major, and the third by Simplex Infrastructures Limited, a Rs 4,713 crore engineering and construction company.
Metro Rail officials described the cracks as hairline, mostly invisible to naked eye.
Dayal said surface cracks in concrete are not uncommon and hairline cracks can easily be repaired using different techniques.
“Indian standard codes for design of reinforced concrete structures allow and permit tension cracks within limits,” Dayal said.
“There is no need to panic.”
But Delhi will take some convincing. It was a crack that led to the Zamrudpur collapse.
The engineers had patched it up and given it the go ahead when in fact the pillar should have been pulled down completely.
Sreedharan had later said that his own gut feeling was to pull down the pillar.
But he allowed himself to be persuaded by his officers to carry on after a patch-up job.
A committee headed by Shirish Patel, a private consultant with expertise in structural engineering, will be taking a closer look at these pillars, as part of his brief to survey all cantilever pillars after the Zamrudpur accident.
As a measure of Metro's famed thoroughness, Dayal said, a similar inspection of pillars and structures was carried out in Phase I, which has been operational for some years now, consisting three lines covering over 65-kilometres.
“A complete span over the Yamuna was rebuilt after the engineers found some problem with that,” Dayal said.
They are ready to do the same if these fresh cracks turned out more serious than expected.