Large landslide hits important transit route at Düzce Zonguldak, Turkey

A large landslide due to a retaining slope failure occurred on a highway at Düzce Zonguldak, Turkey on March 26, 2021. 

The Düzce Zonguldak highway, which is one of the important transit routes connecting Düzce to the Black Sea, collapsed following a night of heavy rains.

According to local reports, an 85 m (279 feet) stretch of the road was damaged.

Governor Cevdet Atay said he has examined the affected area and a temporary service road will be built on the side of the collapsed road. 

"We talked to our Deputy General Manager of Highways. A temporary service road will be built on the side of the collapsed road. It will take four days to build the estimated road."

Atay noted that the road was an important route, so works will be ongoing rapidly. "It is a road connecting Ankara and Zonguldak and an important road in terms of tourism."

Dr. Dave Petley of The Landslide Blog noted in his analysis that there was a retaining wall failure on the highway and described the event as 'unusual.'

"It is interesting that the road has been built across a topographic depression on an embankment made from the fill. I am no expert on retaining structures – is this a mechanically stabilized retaining wall? The wall has slumped spectacularly," he wrote.

Based on the images of the landslide, Petley suggests that there was a build-up of excess pore water pressures in the fill, implying inadequate drainage either due to poor construction, design, or maintenance. 

"Clearly, reconstruction of this highway is going to be a substantial task.  If the failure is the result of a design, construction or maintenance error then other sections of the road may well be at risk too."

Featured image credit: Ihlas News Agency/YouTube