CERN, the European Laboratory for Particle Physics, was established in 1954 and has progressively developed a system of tunnels and caverns in which the research experiments are Conducted, being used by more than 6500 scientists world-wide. In late 2000, CERN have shut down their existing particle accelerator, the Large Electron Positron (LEP) machine, which is installed in a 27 km long tunnel, between 50 and 100 m below ground surface. The existing system will be replaced by the Large Hadron Collider (LHC), which shall start its operation in 2005. The LHC machine will use all the existing LEP underground structures but will also require substantial new surface and underground facilities. The two new detectors, the ATLAS at Point 1 and the Compact Muon Solenoid (CMS) at Point 5, will be larger and more complex than any built to date. The new detectors, weighing up to 15.000 tons, will be installed in newly built caverns. The LHC works at point 5 include two large shafts, two major parallel caverns, separated by a 7 m wide concrete pillar, with a total span over both caverns of more than 50 m. The works are complemented by a system of secondary tunnels and caverns. The geology consists of around 50 m depth of water bearing moraine which is overlying approximately 20 m of molasse above the cavern crowns, which consists of horizontally bedded marls and sandstones. The design involved detailed 2-dimensional and 3-dimensional analyses including load cases like swelling and creeping of the rock mass. The shafts have been constructed with ground freezing, primary insitu concrete lining, waterproofing membrane and secondary slipformed concrete lining. The 7m thick concrete pillar was then excavated and backfilled with concrete in advance of the excavation of the two caverns. Cavern construction includes primary support by shotcrete lining and rockbolts, which will be followed by waterproofing membrane and secondary insitu concrete lining. Due to the extraordinary size and the three-dimensional complexity of the openings, the challenging geology and the adjacency of the existing structures, which had to be partly operating during the early construction phase, the new underground structures are beyond precedent experience and on the limit of feasibility, presenting a real challenge to designers and Contractors.
The European Laboratory for Particle Physics (CERN) is the worlds largest research laboratory for particle physics. Founded in 1954, CERN is supported by 19 member states. The laboratory has over 2800 permanent staff and is used by more than 6500 scientists of world-wide 80 nationalities. The laboratory facilities themselves are located at the Franco-Swiss border adjacent to Geneva airport. It includes a series of linear and circular particle accelerators, which are hosted in tunnels in a depth between 50 and 100 m. The main Large Electron Positron (LEP) accelerator, which is operating since 1989, has a circumference of 26.7 km. The older Super Proton Synchrotron (SPS) has a circumference of 6.9 km and is connected to the LEP at experimental Point 1.