Proceedings - Fifth International Conference & Exhibition on Piling and Deep Foundations, 1994, Bruges, Belgium, (DFI)
Friedrichstadt Passagen Project, Berlin. Deep excavation for multi-basement commercial and car parking facilities
G. Tamaro, A. Brand, C. Sanger & C. DeBenedittis
The Friedrichstadt Passagen Project is located in the “Stadmitte” Section of the former east zone of Berlin and covers three city blocks. The project replaces a partially completed East German development. Friedrichstadt Passagen is the largest excavation and foundation construction ever undertaken in Berlin to the 15 m depth necessary to construct the four underground commercial and parking levels. Construction in Berlin is hampered by severe groundwater conditions. Water is only 3 meters below grade and is the aquifer used for Berlin’s public water supply. Dewatering requirements are strictly controlled by the Senatsverwaltung fur Statentwicklung und Umweltschutz (local environmental planning authority) which limits total volumes of dewatering permitted at individual projects. These quantities are extremely low and cannot be met utilizing conventional construction methods. Four different construction schemes, all utilizing slurry wall construction methodology, were presented for bid. Three of these schemes required installation of a slurry wall to an impermeable layer at a depth down to 50 meters. The fourth scheme contemplated a horizontal grout blanket and a shallower slurry wall. Horizontal water cutoffs such as grout blankets or tremie seals are a preferred method in Berlin but have proven not to be effective in many instances. All four schemes were presented to contractors for bid negotiation. Existing deep foundations on the site required that the cutoff wall be installed within the street right of away. Costs considerations, site constraints and permit requirements dictated that the cutoff wall be constructed using a mixture of cement and bentonite with structural capacity obtained by reinforcing the upper 20 meters of the wall with heavy steel sheet piling. Soil anchors were used to laterally support the sheet piling. A permanent reinforced concrete basement wall was then constructed within the property limits. The foundation mat was temporarily held down with tiedown anchors in order to permit early shutdown of the dewatering system.
|article #835; publication #36 (IC-1994)|