FAIR – New International Accelerator Facility

The project involves building eight ring accel­er­a­tors with a circum­fer­ence of approx­i­mately 1,100 m, two linear accel­er­a­tors and 3.5 km of beam tubes at depths down to 17 m, all covering an area of around 20 hectares, with an embankment of up to 15 m height acting as a radiation shield to cover the equipment.

We have been commis­sioned with all of the geot­ech­ni­cal consulting and planning services as well as on-site construc­tion supervision for the project. Combined pile-raft foundations have been planned for all of the buildings except the accelerator ring. We used 3D finite-element calcu­la­tions to investigate the load-bearing and deformation properties of the subsoil under future load conditions, with a load test on a bored pile at 60 m depth and test filling to improve planning and costs. This resulted in 1,350 piles at a depth of up to 62 m and 60,000 m in length completed within just 14 months – exceptional performance given the location of the construc­tion site in a water reserve and the various require­ments applicable to the site.

The previous construction stage involved the early preparation of a deep excavation down to around 19 m below ground, which required partly lowering the groundwater for protection. Secant pile walling with beam supports was used to shore up the excavation area. The excavation pit covered around 57,000 m² of construction area in this section, and approximately 880,000 m³ of soil was excavated for intermediate storage in separate storage areas before being used for backfilling after shell construction.

Currently, the shell construction work is being completed in two of the three construction areas. The installation of underground pipework on a large scale is still pending so is the finalisation of the terrain modelling by reinstalling the excavated soil. The backfill around the research buildings will be raised to a height of around 14 metres above the original ground level. CDM Smith is currently carrying out quality monitoring as part of this process. Parallel to the exterior work, the technical interior work with the research facilities is also progressing.