CERN's LEP - Large Electron Positron Storage Ring

The European Research Organisation CERN built the LEP - Large Electron Positron Ring - LEP - completed in 1988 - 27 km long underground ring for accelerating, storage and collision of electrons and positrons as well as the relevant facilities for experiments. The 19.3 km long main tunnel was driven by 3 tunnel boring machines (TBMs) at depths of 50 to 140 m in molasses. Roughly every 3.4 km, test and equipment caverns as well as access shafts are set up. 5 of them are large-scale cavern facilities with a system of chambers, galleries and shafts with various diameters and dimensions. As the molasses has a strong inclination to weathering and small breaks in the roof could not be excluded, a reinforced concrete support was first of all installed. The galleries with a total length of 5,500 m have different cross-sections and were therefore driven via blasting or with road headers. In accordance with the geological conditions, various methods were selected for sinking the shafts. Only in the case of 5 shafts was it possible to install concrete rings with a wall thickness of 40 to 70 cm immediately as the final support at heights varying from 1.5 to 3 m. 6 shafts were built using curtain walls, a further 5 shafts protected by a freezing well with freezing depths up to 65 m. The caverns are connected via a large number of shafts, tunnels and lateral chambers. The cavern crowns could not be driven by blasting, in the bench and base zones up to a distance of 1 m from the excavated profile. The remainder was excavated by roadheaders.

Country: France/Switzerland
Region: France/Switzerland
Tunnel utilization: Other
Type of utilization: Research
Client: CERN - European Research Organisation
Main construction method: Trenchless
Type of excavation: Tunnel boring machine (TBM)/Drill-and-blast/Roadheader
Tunnel total length: 19.300 m; 4,000 m
Construction start/end: 1983 till 1988
Opening: 1988