Following Saturday’s cave-in on Poonamallee High Road, experts have raised concerns about the quality and maintenance of the road. If proper measures are not taken to check the quality of the soil, the chances of another cave-in at the same spot are high, they cautioned.
“The authorities concerned must go deep, dig out and replace all unsuitable soil and gravel and have a soil compaction test to ensure the soil is not weak and there is no displacement. Else, the same place might cave in again,” said a road design expert on condition of anonymity.
There are two possible reasons for the cave-in — water might have seeped into the soil from underground pipeline leakages causing it to become weak; or the lack of a proper soil compaction test after earlier underground work. Another well-known expert in Metro Rail projects, who also did not want to be named, said the settling of soil because of tunnelling may have lead to this incident.
“This settling can happen even five years after the tunnelling is complete. Extreme care needs to be taken before tunnelling is carried out. Otherwise, the after effects may last for a while,” he said.
Impact of tunnelling
S. R. Gandhi, former head of the department of civil engineering in IIT-Madras, and director, S.V. National Institute of Technology, also feels tunnelling work could have led to the cave-in. “It is difficult to comment without inspecting the site. This can happen during tunnelling. But now that they say tunnelling work is complete, one possibility is that the soil on top may have escaped into the tunnels if their lining is damaged.”
