L924 Fellerstrasse, Velbert

A heavy rain event in mid-July 2021 caused significant damage to the road body of the L924 – Fellerstrasse in Velbert. As part of the road reconstruction project, PORR was contracted to secure the slope using soil nailing and a jetcrete shell.

The Felderbach stream, which runs parallel to Fellerstrasse, expanded into a raging torrent after the flooding in the summer of 2021, undermining and severely damaging the road. The structural safety of the road body was no longer assured, as a section of the embankment had ruptured. The damaged site had to be restored and a perpendicular bored pile wall established along a central stretch to ensure that the road would be protected if the river were to break its banks again in future.

Specialist civil engineering expertise in limited space conditions

There was not enough space on the Fellerstrasse site to manufacture the bored pile wall. To resolve this issue, our specialist civil engineering experts had to remove enough material to bring the embankment down to a height of around 5m,

and then use soil nailing methods and a jetcrete shell to secure the slope – all within the planned construction period. The jetcrete method can be adapted to suit any topographic situation. In combination with soil nailing, this procedure protects the slope and prevents falling scree and landslides. PORR was able to supply general type certification for the soil nailing system, and the task of executing these works was a safe, secure and routine procedure for our team. The process was completed quickly and economically.

The slope securing measures extended to a height of approx. 5m and were implemented in four separate locations. Each section was stabilised with 7.25m-long soil nails driven into a 25cm-thick reinforced jetcrete shell. Owing to the property ownership situation, we were not able to construct an access road along the side of the valley. As a result, the only access to the construction site was via the narrow bottleneck of Fellerstrasse. This difficult situation added to the challenge of working on the construction site, but the hurdle was successfully overcome via constant and close consultation between all project participants.