Due to a decrease in the sewage volume and shutdown of a treatment plant, Berlin’s underground sewage system had to be re-routed. The project included the construction of a 3,850-meter-long sewage tunnel. The three-meter inner diameter allowed for an installation of two sewage pipelines. The tunnel underpassed densely-populated residential areas, industrial zones, forests and parks as well as a former airport. Metro and long-distance railway systems were also crossed. The machine had to master a curve radius of 350 meters along the tunnel sections with lengths of 1,800, 1,200 and 850 meters.
An AVND3000AH with segmental lining was employed during the project. To master the drive through complex geological formations including sand, stones and marl, the machine was equipped with a mixed-face cutting wheel comprising disc cutters, cutting knives, peripheral buckets and a jaw-type crusher in order to reduce the risk of cloggings on the cutting wheel to a minimum. The slurry tunnel-face support allowed for safe excavation works at a depth of 25 meters. The excavated material is removed via a 250-mm discharge line. The micromachine started its underground mission in Berlin in May 2001. The jobsite team achieved best daily performance rates of up to 26 meters and a breakthrough on June 10, 2002.