Two new caverns for LHC experiments: ATLAS and CMS

The LHC will utilize much of the existing infrastructure already constructed for the LEP. However, to house the new ATLAS and CMS detectors, two huge cavern complexes are required at Point 1 and Point 5 on the LEP. The civil engineering design criteria for the two caverns are presented. Attention is directed to the decisive constraints for the design, such as adverse geological ground conditions, the three-dimensional complexity of the shafts, caverns and tunnels, and the existing LEP structures in the vicinity of the new works which remain operational for the first two years of the project. the paper will demonstrate the different basic requirements of the new underground structures at Point 1 and Point 5. The comparison of the two projects from a civil engineering point of view will aim at explaining why different technical solutions have been adopted for the design and construction of these works.