Report says contractor had warned of collapse of Wayanad tunnel hillside at any moment

WAYANAD: Reports say the contractor had warned that the hillside of the tunnel that was hit by a landslide in Wayanad could collapse at any moment. This was mentioned in the report prepared by Dileep Buildcon Limited (DBL), the subcontractor responsible for the construction of the tunnel in Wayanad. The report indicated that the hillside above the north portal of the Wayanad tunnel was already breaking apart.

The report, jointly prepared by DBL Senior Geologist Raju Sagar, GSI A Ramesh

Kumar and Turkish Engineering Consulting and Contracting Authority Engineer Dr H K Singh, pointed serious flaws. The tunnel project has two ports. The south portal is at Anakkampoyil in Kozhikode and the north portal is near Kalladi-Meppadi in Wayanad. The landslide occurred at the north portal, which is the entrance to the tunnel.

Report says

Engineers who inspected the site between June 3 and June 11 found that the soil on the hillside above the tunnel entrance was made up of a very thick layer of loose, silty soil. The hillside was located on a bed of solid rock about 35 meters deep on the left side. This kind of soil drains water poorly. Water gets trapped inside, and the soil grows heavier, weaker and more prone to sliding during heavy rains.

During heavy rains, the soil on the hillside becomes heavier and weaker. This increases the risk of erosion. To hold the soil in place, the company stepped the slope, sprayed a thin layer of concrete known as shotcrete, and installed metal anchoring rods known as soil nails. But by then, the report noted, the slope was already falling. The engineers noticed cracks developing, the earth falling down, muddy water flowing out, and cavities forming inside the soil itself.

The engineers could hear water flowing through the gap between two of the slope’s support levels. This suggests that a waterway has already been constructed underground.

The report warned that this type of internal erosion would quickly weaken the slope and lead to a sudden collapse. The report also pointed that the safety measures to prevent this collapse were ineffective. The report also states that instruments such as piezometers, which measure groundwater pressure, were not installed. These are instruments that warn of impending slope collapse.

Trial blasts were carried out in the tunnel on June 5, 6 and 11. Cracks in the slope were already visible at this time. However, the report concluded that the shaking caused by the blast was within safe limits and that the crack was caused by heavy rain rather than the blast.