The project:
Construction of the north-south urban railway, Cologne, south section
Executing companies:
Wayss & Freytag Ingenieurbau AG
Ed. Züblin AG
The section is about four kilometres long. By far the largest section of the route is underground in two single-track tunnels that run parallel to one another.
First problem:
Slot walls up to 45 metres in depth were created. During the building phase the slot walls were filled with bentonite support fluid. In order to cast the slot walls, the ratio of sand in the bentonite must not be greater than 3%. For this reason, the bentonite and sand mixture is pumped to a separating system. There the sand part of the mixture is filtered out, and the regenerated bentonite suspension is reused.
Our solution:
Use of a GPN3-80 agitator pump mounted in a slot wall cage.
Second problem:
Two shafts were drilled near the Old Market (Alter Markt). From here the foundations of the adjacent residential buildings were stabilised. In doing so, various cross drillings are drilled to a depth of up to 50 metres depending on the shaft. Next, the boreholes are injected with a cement suspension. In the case of the boreholes as well as the injections the slurry that collects is diverted out of the shaft using a submersible pump.
Our solution:
Use of an NKZ3-100H agitator pump.
The NKZ series is especially well-suited for pumping abrasive suspensions.
