Steep-slope retention with concrete blocks and Geogrids

Steep-slope retention with concrete blocks and Geogrids

Zarnovica, R1 Highway, Slovakia | NAUE GmbH & Co. KG

A steep-slope retention structure with concrete blocks and NAUE Secugrid® reinforcement enabled the latest section Slovakia’s R1 highway to be built at Zarnovica.

The R1 is one of Slovakia’s central transportation arteries. At Zarnovica, the river bank encroaches so closely upon the road in some portions that only 6 to 7 m of space is available to support construction. This fact makes natural banks along the road impossible, both for logistical and cost reasons and flood concerns. A flood event on traditional embankments might lead to road slipping and failure.

To address the Slovak Traffic Ministry’s (NDS) concerns, the NAUE BLOCK system was selected. Two 120-m-long reinforced wall structures with a grade of almost 90° were constructed. The NAUE BLOCK system utilized concrete blocks for the front elements and Secugrid® geogrid for the primary reinforcement.

Zarnovica, R1 Highway, Slovakia | NAUE GmbH & Co. KG

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Not only is this construction technique more economical than traditional concrete construction, but it can be carried out in simple, efficient steps with a minimum of machines required to perform the work—a fact that was greatly appreciated in the project’s tight footprint.

For Zarnovica, the 20-cm-high wall blocks feature a hollow interior zone that is filled with gravel upon installation.

The Secugrid® geogrid layers were installed 60 cm from one another, creating a uniform system with three gravel-filled concrete blocks along the front face of each reinforced layer. The anchored lengths of Secugrid® were between 4.5 and 6 metres.

During construction, a unique situation was also dealt with. The pile footings for a noise barrier wall were being retrofitted, and this construction in the tight project zone meant that they needed to be driven one metre behind the NAUE BLOCK wall and through the Secugrid® layers. Tensile issues were not a concern, however, as punch-through zones were figured into the relevant Secugrid® geogrid layers. The concrete piles absorb the ground pressure in front of the exterior block face.

Altogether, more than 5,000 m² of Secugrid 40/40 Q1, 20,000 m² Secugrid 80/20 R6 and 1,200 m² of concrete blocks were installed.