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Slope stabilisation “I/35 Hřebeč”

Retaining structures

Project name Slope stabilisation "I/35 Hřebeč" Volume 3.300 m³ expanded clay 8-16 mm crushed Location Hřebeč, Czech Republic Year 2006
Contractor Skanska DS a.s. Designer Ing. Stanislav Štábl Owner/Builder Ředitelství silnic a dálnic ČR


After finishing the highway L/35 next Koclirov a hillside at the north-east entrance of tunnel Hřebeč became destabilized. Bad geological conditions and a sandstone penetrated by water made the whole hillside crashing down, blocking the entrance of the tunnel and caused an accident on the highway. It turned out that a supporting construction with a stabilizing foundation next to the road and a leaning construction without putting too much pressure on the existing hillside would be the best. In addition the construction offers the opportunity for greening. The geological conditions required a careful logistic concept without being a danger or a barrier for traffic.

Why Expanded Clay:

By using expanded clay all of the requirements could be fullfilled. Less stress for the existing material and stable in its own was necessary. With a kind of green plates the stabilization at the edge of the steps could be reached and was the guarantee for greening. The drain aging features make sure that a rising water pressure can constantly be avoided. In these regions the freezing resistance of expanded clay is also necessary and important.


To remediate a slope this application was done for the first time in this way. So it was an interesting project, especially in combination with geotextiles as a kind of reinforcement. After constructing the foundation the new hillside was build up in layers of expanded clay with geotextile covered gabions which were filled directly at the site by blowing expanded clay to the installation location. So a minimum load and a high stability in its own were guaranteed. The material was delivered and stored on top of the hill making a fast application possible.

Key Issues:

Drainage, Earth preassure, and Stability

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