1. Plasma Wakefield (AWAKE) Project Meeting 18 October 2012 Civil Engineering Feasibility Issues for the West Area EDMS 1246170 : John Osborne GS-SE

2. Civil Engineering Studies In August 2012, CERN civil engineering were requested to study the feasibility of housing the AWAKE Project in the ‘West’ Area Studies have concentrated on the idea of ‘deepening’ the invert of the existing TT4 and TT5 galleries, that lead up to the West Hall, Blds 180/183. These galleries are located on the Meyrin Campus, on the French side of the site. They were constructed in the 1970’s, and are located within the Quaternary fluvio- glacial ‘Moraines’. The wall footings of the tunnels extend down to the Molasse Rock, with the tunnel being constructed using the ‘cut and cover’ technique and then covered with the resulting excavation material. It is assumed that the concrete/earth to be excavated requires no special radioactive treatment A specialist design firm has assisted in the ‘trench’ design for ground excavation & support methods (ARUP UK)

3. Proposed area for ‘trench’ in TT4 and TT5 tunnel invert. TT4 TT5 TT61 John Osborne GS-SE Initial CE study was for the TT61, TT4 and TT5 galleries All CE layouts provided by Antoine Kosmicki GS-SE

4. Initial CE feedback on TT61/TT4/TT5 Proposal : Extremely difficult to ‘trench’ under the TT61/TT4 junction area Possible (but technical challenging) to ‘tunnel’ under the load bearing junction area CE requested if ‘trench’ works could be concentrated in the TT4/TT5 area John Osborne GS-SE

5. Civil Engineering Studies : Trench works concentrated on TT4/TT5 area

6. Typical cross section through TT4 ‘trench’ area Depth & width of the trench will determine the design/construction methods, if we enter the Molasse rock, Roadheader required for excavation & shotcrete / rockbolts for rock support. More detailed studies needed to check overall stability. For initial studies, trench assumed to be 3.5m wide by 3.5m deep Space needed for machine/services & transport to be evaluated ARUP UK contracted to evaluate various ‘trenching’ methods John Osborne GS-SE

7. ARUP Option 1 : Minipiles and in-situ slab (no propping) Risk of wall deflections Approx cost = 1.05MCHF (for assumed 100m long trench in TT4/TT5) Estimated construction time = 8 months John Osborne GS-SE

8. ARUP Option 2 : Minipiles and in-situ slab (with propping) Slower construction method Smaller wall deflections Approx cost = 1.15MCHF(for assumed 100m long trench in TT4/TT5) Estimated construction time = 9 months

9. John Osborne GS-SE ARUP Option 3: Propping and ‘full’ excavation Small wall deflections Slow and complex propping Shotcrete & rockbolts required Whole tunnel needs to be cleared for the works Approx cost = 1.13MCHF (for assumed 100m long trench in TT4/TT5) Estimated construction time = 10 months

10. CE Feedback on TT4/TT5 option: Trench works technically feasible Major concern with position of existing Technical Gallery TP1 : the proposed ‘trench’ passes directly through this gallery John Osborne GS-SE

11. Many services pass through this TP1 gallery, including the new EL power supplies for network consolidation John Osborne GS-SE

12. Possible CE Solutions : Deepen the existing gallery and ‘lower’ services, to allow machine to pass over the top Disadvantages : More expensive CE solution The existing gallery would need to have all services removed to allow excavation, and then re- installed. LS2 ? John Osborne GS-SE

13. Possible CE Solutions – Excavate a new tunnel under TT4 or TT5 Advantages : New services could be installed in new gallery during machine operation Disadvantages : Most expensive CE solution ‘Switch-over’ of services would have to be done in LS2 ? John Osborne GS-SE

14. Possible CE Solutions – deepen the trench to pass the machine under the gallery Advantages : No need to divert services in existing gallery Disadvantages : More expensive CE solution and technically challanging to ‘tunnel’ under the existing gallery Radiation issues for existing gallery ? More difficult for machine installation/ access during operation John Osborne GS-SE

15. Other Possible Solutions : ‘ Allow’ new machine to pass through the existing gallery Concentrate trench works on TT5 gallery only Modify TT61 gallery to allow earlier machine ‘height’ adjustment : Not yet studied by CE John Osborne GS-SE Preferred CE Options !

16. Civil Items not considered at this stage Tunnel drainage Where any spoil would be stockpiled Extra shielding required for other facilities (nTOF, West Hall) Building works needed for other systems eg access control, ventilation, electricity etc TT61 CE modifications John Osborne GS-SE

17. Conclusion and Next Steps for CE John Osborne GS-SE Technically possible to ‘trench’ in the TT4/TT5 area (exact depth / width of CE works to be defined) Issue with existing TP1 gallery to be further studied Noise and vibration impact of any CE works to be evaluated 3d CATIA Model needed for the ‘selected’ area, and integration studies carried out to better define the CE works CNGS CE works to be studied