Canal trough bridge, Schwarzach near Nuremberg

As part of the rehabilitation measures for the Schwarzach canal trough bridge near Nuremberg, which carries the Main-Danube Canal across a road and the Schwarzach River, The Stuttgart branch was commissioned to produce four construction pits near the bridge wing walls and to manufacture and test four trial strand anchors in the bridge abutments.

Consulting - planning - building: everything from a single source

PORR Spezialtiefbau offers everything from a single source. This expertise is in demand for the rehabilitation of the Schwarzach trough canal bridge: stranded steel straps were to be used to brace the bridge wing wall as a rehabilitation measure. In order for the bracing to be implemented safely, four construction pits with a depth of around 9m had to be produced at the bridge abutments. Reinforced sheet pile walls were used to secure the longitudinal walls of the construction pit, and soil nailed jetcrete was used for the uphill head walls. In order to ensure that the bridge wing wall was supported during construction, stiffening braces made from steel girders were positioned on three levels to transfer the required supporting force from the sheet pile walls to the bridge wing wall.

Solution for challenging subsoil: the vibro-flushing method

The sheet piles are positioned in the canal embankments parallel to the wing walls of the bridge abutments. The slope makes frame-led vibro-compaction of the up to 13m-long double sheet piles impossible, so the sheet pile walls had to be compacted without a frame. In some areas, hydraulic flushing had to be used when driving the sheet piles in order to break through obstructions in the ground and soil layers that are very difficult to push through. This method is called the vibro-flushing method.

In-house planning expertise

Our fellow engineers from PORR Spezialtiefbau Planung supported the specialist civil engineering team with their planning expertise during the rehabilitation of the Schwarzach Bridge: they took care of the structural analysis of the excavation shoring and the soil nailed jetcrete headwall and were responsible for supplementing the execution technology for the construction pit shoring and soil nailing. Four more test anchors with lengths of up to 50m were successfully installed on the bridge abutments despite the limited headroom and extremely restricted spatial conditions.