A new particle accelerator is being built in Darmstadt. PORR is responsible for the extended structural work in the north facility area.
The contract includes not only the construction of a 1.1km long accelerator tunnel including the vertical building components, but also a transfer building with an underground transfer hall and the main supply building above.
One of the largest and most complex construction projects in the field of cutting-edge international research is currently underway at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt: FAIR (Facility for Antiproton and Ion Research). A new particle accelerator is to be used to create and research matter inside the confines of the laboratory that is normally only found in the universe. Scientists from all over the world hope to gain new insights into how matter is structured and how the universe has evolved – from the Big Bang to the present day.
Several different buildings that are necessary for operating the particle accelerator will be erected on the approximately 20ha site. PORR was awarded the contract for the extended structural work in the north facility area. In order to meet the high requirements, solid reinforced concrete components are being used. The jointless construction method imposes heightened demands on crack limitation and concrete performance.
Most of the structures are solid reinforced concrete constructions and up to 6m thick. The supporting structures for the buildings are made from solid reinforced concrete with reinforced concrete load-bearing exterior walls, access cores and interior columns, and interior walls in reinforced concrete supporting reinforced concrete floors.
The accelerator tunnel will have shallow foundations, while the solid transfer building and the tunnel in the adjacent area of the transfer hall will be founded on a combined pile and slab foundation. The solid components and the complex frame place very high demands on the planning and execution of the supporting framework. Wall-type beams are temporarily supported by solid concrete columns until the load-bearing capacity of the entire system is achieved.
The concrete to be used must have very specific properties. The increased bulk density of 2.35kg/dm³ and the residual water content of 4.5% have led to a formulation that includes basalt aggregate, slow-hardening cement, and high water-cement ratios, placing very high demands on both the workers and the machinery involved in production, transport and processing.
The concrete is produced directly on site with a mobile mixing plant to ensure a continuous supply of 150m³ per hour and up to 3,000m³ per day. PORR will handle over 100 large-scale concreting operations with an average of 1,500m³ of concrete each throughout the construction period. The peak monthly output will be 15,000m³ of concrete, which corresponds to 33,000t of aggregates and cement, and 3,600t of reinforcement. Given that the excavation and backfilling of the construction pit are being carried out simultaneously, 250 lorry journeys per day are not uncommon. A fresh concrete composite system is used to seal the exterior components.
The pipeline construction is also adapted to reflect the dimensions of the overall project. The installation of 10km of steel and HDPE pipelines with diameters of up to 2.0m, along with 25km of cable conduits, which had to be carried out at the same time as the backfilling work, also posed a major logistical challenge.
The project is currently in full swing. The excellent cooperation with PORR Design & Engineering Berlin, Structural Engineering division, and PORR Design & Engineering Vienna, Work Preparation and Structural Engineering division, has helped the construction crews on site to overcome the enormous challenges posed by this major project.
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