CERN

When a particle accelerator grows

The Large Electron Positron (LEP) particle accelerator was located in a 27 km long tunnel 100 m below the earth’s surface. The new Large Hadron Collider (LHC) can generate beams at an even higher energetic level than the previous one. It was installed in the already existing tunnel of the LEP and therefore, the construction of two large underground cavern complexes was necessary.

The assignment of Geoconsult

The large experimental areas of the LHC are located at Point 1 (Switzerland) and Point 5 (France). Point 5 comprises an experimental cavern the 15,000-ton CMS particle detector.Computer systems for the analysis of the experiments are installed in the parallel service cavern. Large shafts leading from the ground surface to the cavern roofs, as well as smaller caverns, access, bypass, surveying and observation tunnels supplement the cavern complex. Geoconsult was part of a British-Austrian-Swiss joint venture for the design of all civil works(preliminary, tender and detailed design) as well as the construction supervision for the underground structures and surface buildings.

Challenging terrain

The size of the cavern structures was beyond the previous experience and the complex geotechnical conditions (overburden of 50 m of groundwater charged moraine and 20 m of molasse rock comprising layers with potential creep and swelling behaviour) presented extraordinary challenges for the design and execution.