Civil Engineering Feasibility Study for CERN's Future Circular Collider-Paper

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CERN’s feasibility study is evaluating a Future Circular Collider (FCC) as a possible successor to the Large Hadron Collider. The proposed collider would occupy a new tunnel roughly 80–100 km in circumference in the Geneva Basin, with a 100 TeV hadron collider as the principal option.<br /><br />To compare potential layouts, CERN and Arup developed a web-based, interactive Geographic Information System tool. It combines geological, topographical, environmental and built-environment data, allowing engineers to assess how alternative tunnel routes affect geological risk, overburden, shaft depth and surface-site suitability.<br /><br />The region’s molasse generally offers favourable tunnelling conditions, although its weaker marls can swell. Limestone is riskier because of water-filled karsts, while shallow glacial deposits can be soft and water-bearing. The study therefore seeks to keep the tunnel mainly in molasse, avoid excessive overburden and deep shafts, and limit impacts on protected areas and settlements. These objectives can conflict: some options cross glacial deposits beneath Lake Geneva, where a minimum depth of 80 m below the lakebed is being considered. Inclined access tunnels may help address unavoidable deep shafts and provide additional construction access.<br /><br />The underground works would include a 97.75 km tunnel, four experimental caverns with 35 m spans, service caverns, and 20 shafts across 12 locations. Major construction challenges include shafts up to great depths through water-bearing deposits and large-span caverns. Potential shaft methods include diaphragm walls, ground freezing and vertical sinking machines; cavern excavation may require staged construction and reinforced-concrete pillars.<br /><br />The tool has helped identify a technically feasible location and improve early design decisions. Further geological investigations and project-wide assessment are needed before a decision on whether to proceed.

Keywords

Future Circular Collider

CERN

Large Hadron Collider

Geneva Basin

geological risk

tunnel alignment

molasse

Lake Geneva

shaft excavation

underground infrastructure