A mineralogical re-use classification model of molasse rock mass in the Geneva Basin

The Future Circular Collider (FCC) aims to become the largest and most powerful particle accelerator in the world located in parts of France and Switzerland. In order to host such an ambitious machine, a tunnel with a length of 97.75 km is currently under feasibility study at the European Organization for Nuclear Research (CERN). One of the study’s main challenge is the handling of more than 9.1 million m3 of tunnel excavation material. As a matter of fact, this requires a sophisticated geo-scientific and technical classification of FCC’s proposed excavated geological units, respectively the molasse rock mass, in terms of re-use and disposal scenarios and to generally considerate its environmental and economic impact. The paper casts a glance at the arising scientific opportunity to classify the excavated tunnel material in future using a mineralogical approach from macroscopic to microscopic scale. Analyses show nickel and chromium minerals within the upper and anhydrite in the upper and lower molasse parts. Nickel and chromium concentrations pollute the molasse rock mass but could imply potential mining as a re-use scenario. Anhydrite likely causes tunnel construction issues when in contact with water. The proposed classification model serves as a link to French and Swiss legislation as well as an European technical guideline concerning re-use of tunnel excavation material on any international construction site. It simplifies and delivers the basis for future contractual models from a client’s and contractor’s perspective under conditions and protection of national, international and European Union legislation.