Duct works Distelfeld

Structural verification for the new building of a main sewer

The existing waste water system of the city of Neuwied used to reach its limit in the past during heavy rainfall. To prevent potential flooding and thus damages the Servicebetriebe Neuwied (SBN) built a new sewer from the business area “Distelfeld” to the Rhine. This main sewer intended for relief is not only meant to protect the existing sewer system but also the inner-city sewage treatment plant from capacity overload when rainfall events occur.

In the future the rainwater from the business areas „Friedrichshof“ and „Distelfeld“ will be discharged into the Rhine through the new sewer DN 2000 with an overall length of 2,7 km. Since the majority of the distance is a built-up area and the sewer crosses several streets as well as an eight-track railway system, the bigger part of the pipes (2,5 km) haven been laid using the pipe jacking technique. The connection to the existing sewer system is achieved by two flow-dividing structures.

The structures have been executed using waterproof in-situ concrete with wall thicknesses of 25-80 cm. For the excavation support system of the up to 11,5 m deep pits not only sprayed concrete sheet piling but also soldier pile walls and embankments were utilised. Works in pits up to 6,0 m below ground water level as well as the high demands on water impermeability of the overall structure were special challenges. Another special feature is using the pipe jacking technique with partly very small radiuses (R=150 m). This could be realised using hydraulic joints as means of pressure transfer.

ZPP or the predecessor company has been acting as a structural design verification engineer. Verification included the tubes, 10 shaft structures including the two flow-dividing structures and one slide structure as well as necessary pits. In addition to the structural verification random inspections of the execution of construction work in the pits and the structures on site were conducted. As a technical consultant ZPP or the predecessor company was able to contribute its competences – e.g. during checking peculiarities in execution or a changed building schedule.