DIGGING UNDER DUESSELDORF

The article describes two unusual projects, a riverside road- tunnel system and an extension to the underground railway network. Much of the new road is of subsurface double deck construction, each deck carrying two traffic lanes, and is built in a narrow space between the river bank and some large important buildings. The previous heavily congested road will be replaced by a riverside park with pedestrian areas. Diaphragm walls were constructed by boring and cutting from the surface above the high-water level. The slots were then filled with bentonite slurry which was displaced from the bottom by special concrete. A concrete floor slab was built at the base of the upper tunnel and the lower tunnel was driven underneath using compressed air to prevent ingress of river water. The foundations of sensitive nearby structures were underpinned. Deep-level car parks are also being constructed. The 1.7km twin track U-Bahn rail extension is divided into two contracts which included the construction of two underground stations where an International Trade Centre is planned. Icewall protection was used for a 40m long drive by a partial extraction method. A range of protection methods were used for an 80m length with about one metre clearance below the basements of buildings.