Internal report flagged distress signs before Wayanad tunnel landslide
What's the story
A recent internal report by Dilip Buildcon Limited (DBL), the sub-contractor for a tunnel project in Kerala's Wayanad, has revealed alarming details about the conditions at the site before a deadly landslide. According to NDTV, the report, co-signed by DBL senior geologist Raju Sagar, Geological Survey of India's A Ramesh Kumar, and Turkish Engineering Consulting & Contracting Authority Engineer Dr HK Singh, indicated that the hillside above the North Portal was already breaking apart.
Soil analysis
Distressing details from report
A geological and geotechnical assessment of the North Portal found that the hillside was made up of a thick layer of loose, silty soil about 35 meters deep on the left side of the slope. This type of soil drains water poorly, making it prone to sliding during heavy rains. Despite safety measures like cutting the slope into steps and using shotcrete and soil nails, the slope was already failing when engineers inspected the site between June 3 and 11.
Erosion concerns
Internal erosion, hidden risk factors
The report also highlighted internal erosion as a major concern, with engineers hearing water flowing underground. This hidden erosion can quickly weaken a slope and lead to sudden failure. The left-hand slope was identified as carrying a distinctly higher risk than the right, with the report stating it "may culminate in sudden slope failure at any time" under prevailing rainfall conditions.
Safety failures
Safety systems not functioning properly
The report also pointed out that safety systems meant to prevent such collapses were not functioning properly. Drainage holes drilled into the slope were ineffective, and early warning instruments had not been installed. Trial blasting for the tunnel took place on June 5, 6, and 11, when the slope was already showing distress. However, recorded blast vibrations were within safe limits according to the report.
Recommendations issued
Report flagged hazards, recommended gabion walls
The report recommended several measures to mitigate risks: building gabion walls along the left-wall slope, covering bare earth with protective matting, and cutting lined channels to carry rainwater away from the slope. It also flagged a concrete-mixing plant near the slope as a hazard. When contacted by NDTV, an engineer with Konkan Railways said, "We completely stopped work in this portal after the report." The report had predicted the calamity six days before the District Collector's June 20 stop-work order.