25 m high green steep wall

Situation

The development of a new residential area, Wohnpark Hellweg in Iserlohn, in the immediate vicinity of the A46 motorway, necessitated the construction of a combination of a retaining wall and a noise barrier. The retaining wall served to bridge an 18-metre difference in ground level and create sufficient space for the planned residential park.

Solution

The client opted for a geosynthetic-reinforced earth (GRE) structure with layer-by-layer reinforcement using geogrids. The extreme total height of up to 25 m with a slope of 80° (noise barrier) and 90° (retaining wall) was, at the time, unique in Germany for this type of construction. To secure an existing retaining wall, up to 9 m high and subject to heritage protection, and to avoid costly demolition, the KBE was constructed in the lower third as an earth pressure retaining structure directly behind the concrete wall. Right-angled bent structural steel mesh was used as permanent formwork. A 20 cm gap was left between the steel mesh face and the concrete wall, which was filled with mineral wool. The construction of the green retaining wall begins approximately 5.0 m set back from this vertical retaining wall. Angled steel mesh was also used here. The use of an erosion control and greening mat with integrated grass seed proved to be the optimal solution for the primary greening. The secondary greening was achieved through targeted planting.

Advantages

• A highly flexible solution in terms of design, technology and adaptation to local conditions
• Simple construction
• Minimal settlement and deformation; not susceptible to potential differences in settlement
• Excellent integration into the landscape
• PVA geogrids allow the use of locally available recycled concrete
• A very cost-effective solution