THIRUVANANTHAPURAM: Two weeks after a portion of the wall of an embankment constructed at Punnakulam near Vizhinjam of the under-construction NH-66 bypass was damaged following heavy rain, a team of experts from IIT Palakkad have recommended to L&T Constructions, contractor of the project, to reconstruct the reinforced wall on the Mukkola-Karode stretch.
They said after visiting the site that the wall must be reinforced with additional drainage and strengthening measures taken based on the preliminary findings. They want the wall to be reconstructed before the next monsoon.
The IIT Palakkad prepared the report for National Highways Authority of India (NHAI) after studying the damage. The damaged portion of the reinforced wall poses a danger to the pedestrians and motorists using the service roads. Hence, NHAI had assigned IIT Palakkad to study and submit a report on the reasons for the damage that occurred for the third time due to rain.
The rectification of the damage is likely to restart this week based on the findings, NHAI sources said. A day after the damage was reported, the rectification work was stopped by local residents alleging that it would worsen the situation.
Sources close to NHAI said the IIT team will submit the report soon and the rectification work will begin accordingly. As per the report accessed by TNIE, the IIT team recommended that the present alignment of the panels (concrete blocks) of the wall should be measured. During the removal of the panels, the wall body (backfill soil, reinforcements, drainage connections, Geocomposite and connections) should be examined, it recommended.
Reasons for damage
L&T Construction informed the IIT team that the damage occurred after the water started seeping into the Geocomposite, thereby reaching the bottom panel rapidly. As per L&T, this water was mixed with the soil fines from the embankment soil. As the reinforced wall drainage (in the form of PVC pipe) is not designed for such a large volume of water, the water started accumulating inside the panel. As the rain continued for more than two hours, the accumulated water started exerting pressure on the bottom panels from inside which were not designed for such pressure. Finally, one panel gave way and got dislodged, the report stated.
Features of stretch
Incidentally, the 16.3km concrete highway from Mukkola to Karode is likely to be commissioned in May. Construction of only 1.2km is pending, including the 500-metre-long stretch at Punnakulam. The retaining wall is around 15 metres high from the ground. Earlier, there was a suggestion that pillars should be erected rather than constructing the retaining wall on either side. This is because retaining walls pose a higher risk as any small crack formed in a wall could result in a possible danger.
Major findings in the report
One concrete block of the wall got dislodged
Some of the adjacent blocks got misaligned while the others remained in place
Geogrid reinforcements at the distressed location appeared to be broken at the connection
Geocomposite drains were damaged
Perforated drainage pipe was broken
Backfill soil was lost through the opening of dislodged concrete block