Abstract

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.

1 Introduction

Within the last decade, the European Organization for Nuclear Research (CERN) initiated several feasibility studies to build a future collider facing the physical challenges of the 21st century (Zimmermann 2015). A new collider should aim to supersede the current 27 km Large Hadron Collider (LHC) in terms of energy and luminosity. Currently, the High-Luminosity Large Hadron Collider (HLLHC) project is upgraded to prepare for the next collider (Acar et al. 2017). However, looking beyond the next decade, a more powerful machine will be required. Hence, study efforts resulted in the final outcome named the Future Circular Collider (FCC) located in the canton Geneva, Switzerland and the French region Auvergne-Rhône-Alpes as depicted in Fig. 1. Its scope has been extensively examined with the intent to start physical measurements by 2040 (Abada et al. 2019a, b, c). The remaining time gap tends to investigate the subsurface being part of the geological Western Alpine Molasse Basin in terms of environmental, civil engineering and geological considerations and feasibility.

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