Sewer Winterhude, Hamburg

The Free and hanseatic City of Hamburg is building approx. 20 km of transport and feeder sewers and 15 retention basins in order to relieve the load on the River Alster and its tributaries from overflowing combined water. These transport sewers are located beneath the sewer and collector network and are linked to them at suitable points so that sewage can flow without backpressure through the existing network to the main treatment plant. Combined water, which can no longer be handled following heavy rainfall, flows into retention basins. The first section of the overall project to be completed was the Winterhude transport sewer, construction lot 1. It comprises an entry shaft, a 500 m long collector with an internal diameter of DN 3500 as well as various control shafts, transitional structures and connecting lines. The tunnel is some 5 to 8 m below the ground surface, passing only a minimal distance below old trunk sewers, high-voltage underground power lines, distance-heating tunnels and shafts as well as buildings with shallow foundations, which are sensitive to settlements. Beneath filled, extremely loosely bedded overlying strata, the route passes through largely loosely to very compactly deposited fin e and coarse sands as well as gravels. The groundwater is located some 2 to 4 m below the ground surface. On account of the extremely tricky marginal conditions, the tunnel was driven via a shield with a fluid-supported bentonite face. The client decided in favour of a Thixschild, which has a cutter to excavate the soil, which is then conveyed by the bentonite suspension to the surface, where it is separated again from the bentonite in a special facility. The exact regulation of the bentonite pressure in the shield chamber is assured by fully automatic control of the feeder pump. The maximum pressure deviation amounts to only 0.05 bar even given extremely difficult ground and excavation conditions. The shield chamber has been dimensioned generously enough so that obstacles/ boulders can be collected en route so that the chamber does not have to be entered all that frequently. To enter the chamber, the bentonite must be drained and the chamber filled with compressed air. The breasting support plates are extended to form additional mechanical support for the face. A lock was installed in the floor so that rocks up to a size of 50 cm can be recovered without entering the shield chamber. The section was completed by pipejacking. Reinforced concrete pipes, 3.6 m in length and with 33 cm thick walls were installed. The pipes were lined at the plant with a 3 mm thick, hard PVC foil in order to protect them against corrosion. The foil is attached to the concrete at the rear with approx. 10 mm high T-shaped anchors. The anti-corrosion lining was only installed in the roof and wall sections up to 270°. After the tunnel was completed, a channel was incorporated in the base section.

Country: Germany
Region: Hamburg
Tunnel utilization: Utilities
Type of utilization: Sewage
Client: Freie und Hansestadt Hamburg
Main construction method: Trenchless
Type of excavation: Shield machine (SM)
No. of tubes: 1
Tunnel total length: 500 m
Diameter: DN 3500
Pipes: Concrete B 45
Wall thickness: 33 cm
Inner lining: PVC on 270°
Construction start/end: 1986 till 1988