Back-anchored gabion wall along the A3

Situation 

As part of the six-lane expansion of the A3 between Frankfurt and Würzburg, it became necessary to construct a very high retaining structure to secure the road cross-section to be widened on the valley side. The tender for the construction work to be carried out in a topographically challenging location near the Rohrbrunn (Haseltal) junction was issued in 2010 by the North Bavarian Motorway Authority.

Solution

The construction of the retaining structure using a plastic-reinforced earth (KBE) system proved to be the most environmentally friendly and cost-effective of all the options examined by the client. Gabion baskets filled with frost-resistant and compressive-strength limestone form an aesthetically pleasing facing for this sophisticated retaining structure. The gabion baskets were installed in parallel with the construction of the load-bearing structure, which was constructed using geogrids in a cushioning arrangement. A geotextile was used in the overlap area of the geogrids to provide additional erosion and run-off protection. These impart additional tensile strength to the fill soil and relieve the front face of horizontal earth pressure. The connection to the cushion wall was achieved using corrosion-protected steel grids. These were connected to the gabion baskets via plug-in fasteners at vertical intervals of 1.0 m (height of gabion basket) and anchored back into the intermediate layers of the cushion wall. Due to the high technical and operational requirements placed on the structure, a complex monitoring system was installed for continuous surveillance.

Advantages

• Cost-effective construction
• Aesthetic and natural-looking surface
• Ecologically sound concept
• Use of flexible geogrids with integrated sensors for structure monitoring
• Can also be used on hard-to-access construction sites
• Resource-efficient and noise-absorbing
• Short construction time compared to conventional support structures
• IVG product certificate eliminates the need for incoming materials testing