MDI 9 th Meeting - 22 nd January 2016 FCC Experimental Caverns - Feasibility and Excavation C. Cook (GS), J. Osborne (GS),

Introduction FCC schematic Report: Comparison of 100km FCC options (AMBERG) Excavation techniques for experimental caverns and shafts Next steps

FCC Schematic 100km ring 4 Experimental points 8 Access points 8 RF tunnels 2 beam dump tunnels 2 injection tunnels Service caverns – 90 x 20 x 13 (LxWxH) w. single access shaft – diameter tbc

Report contents Geological and Geotechnical conditions Risks applicable to FCC options. Basis of 5. and 6. First look at excavation methods for tunnel, shafts and caverns based on varying geological conditions Comparison of options Introduction and description of options Conclusion

Construction of shafts Experimental Shafts If moraines is firm, cohesive or consolidated => conventional excavation. Lattice girder rings, shotcrete and steel mesh as support If loose or below water table => pile walls up to 25m deep, diaphragm walls >25m Through moraine layer Through molasse layer Drill & blast recommended. Support similar to moraines but less required

Access Shafts Excavation through moraines is the same as for the experimental shaft. For the molasse, shaft boring machines or drill and blast are possible. Drill & blast may prove the less risky choice (flexibility, previous projects failed with machine, non-specialised workfoce). Construction of shafts

Experimental Caverns Excavation sequence based on ‘good’ geological conditions (stable rock) Support: rock bolts, lattice girders and reinforced shotcrete Excavation of caverns

Experimental Caverns Excavation sequence based on ‘moderate’ geological conditions (Flysch and soft clay rock) Support: micro piles, rock bolts, lattice girders and reinforced shotcrete Excavation of caverns

Experimental Caverns Excavation of caverns

Service and access caverns Service Caverns with a span of 20 m and Access Caverns with a span of 15 m Excavated like the Experimental Caverns, in partial sections An important point for planning the location of the Service Cavern is the stability of the rock pillar between Experimental Cavern and Service Cavern This rock pillar has to transfer the additional burden of half of the two caverns and has to be probably 40 to 50 m wide. The necessary dimension can be determined only after exploring the geological conditions in this area. Caverns can be closer together only with concrete pillar (as with CMS) Excavation of caverns

6. Comparison of FCC options Data

6. Comparison of FCC options Data

Report Conclusions Conclusion “It can be concluded that the foreseen caverns and shafts, with their proposed dimensions, are possible to excavate under the given geological circumstances… it will become more a question of time and costs than constructability.” “neither engineering nor logistic limits are met although special equipment with limited availability is needed for certain structures.” “With the information available so far, no changes of the project, with respect to the given dimensions for shafts and caverns, are mandatory.” “it is strongly recommended to execute further geological and geotechnical investigations. Based on the results of these investigations, additional risks can be detected or currently defined risks can be adjusted for each option.” “A final recommendation of one of the two options is very difficult to make at this stage of the project and would lead to a premature decision based on insufficient data. However, if a decision had to be made by CERN based purely on the available data, the Intersecting Option would seem the better choice due to the avoidance of the Flysch section in the Pré-Alps with high overburden and squeezing potential. In addition, for this option, the excavation of the Experimental and Access Points are assumed to lie entirely in Moraine and Molasse with good rock conditions." Note: CE recommendation remains 93km Option 1. This was outside the scope for Amberg’s report

Experimental points -Next steps Drawings for: Experimental cavern Experimental shaft Service cavern Service shaft General arrangement – inc. connection tunnels Working with MDI on: exp. cavern plan, crane, metallic structures, equipment in exp. & service cavern, separation of caverns, connection tunnels etc.

Access Shaft PM54 12m diameter

Access Shaft Concept – double lift Diameter tbc Pressurised Stairwell Main lift (pressurised) Backup lift (pressurised)

Access Shaft Concept – magnet shaft Oblong, dimensions TBC Main lift (pressurised) Trémie Pressurised Stairwell