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LAGUNA at Fréjus LAGUNA/LAGUNA-LBNO General Meeting March 3 th -5 th , 2011, CERN

LAGUNA at Fréjus LAGUNA/LAGUNA-LBNO General Meeting March 3 th -5 th , 2011, CERN Eng. Francesco Amberg. Current situation – General plan view. LSM Underground Laboratory Modane. Road tunnel (1974-78). Railway tunnel (1857-70). Longitudinl section. > 1700 m rock overburden.

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LAGUNA at Fréjus LAGUNA/LAGUNA-LBNO General Meeting March 3 th -5 th , 2011, CERN

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  1. LAGUNA at Fréjus LAGUNA/LAGUNA-LBNO General Meeting March 3th-5th, 2011, CERN Eng. Francesco Amberg

  2. Current situation – General plan view LSM Underground LaboratoryModane Road tunnel (1974-78) Railwaytunnel (1857-70) Longitudinl section >1700 m rock overburden 6,6 km 6,2 km 12.8 km

  3. Current situation - LSM underground laboratory Modane External LSM building km 6.0 km 7.0 6,6 km 6,2 km A cavityofabout3500 m3 in the middle of Fréjus Road Tunnel in frenchterritory

  4. New safety tunnel (currently under construction, expectedconclusion 2014) LSM Underground Laboratory Modane Safety tunnel Cross connection

  5. Location of new detector near existing infrastructure LSM (1982) Safety tunnel (2009 – under construction) New detector (examplewithMEMPHYS) Road tunnel (1974 – 1978)

  6. Trias Series Geology Calcareous schists

  7. Assessment of rock mass properties - Usual situation (a priori) Laboratory tests Intact rock properties Modulus of elasticity E=50 GPa Poisson’s ratio n=0.2 Density r=2.7 t/m3 Compressive strength sci=100 MPa Empirical methods Rock mass properties Properties of discontinuities Friction angle j=35/23° Cohesion c=150/15 kPa Number ? Orientation ? highly uncertain

  8. Assessment of rock mass properties – Situation at Frejus (a posteriori) In situ large scale tests Modulus of elasticity Edin=15 GPa Compressive strength sci=15/4 MPa Rock mass properties Excavation of road tunnel Convergence monitoring Extension of failure zone around tunnel Discontinuities (number, orientation, quality) Back analysis Reduction of uncertainties Others properties Water inflow Rock mass temperature Advantage of Frejus Intensive analysis of tunnel behaviour during construction (and well documented)

  9. Back analysis of road tunnel (time-dependent behaviour) • Definition of time dependent parameters: • Short term: from tunnel behaviour 35 m behind the face (5 days) • rock support provided only by systematic bolting • (convergence 6-9 cm) • Medium term: from convergence before casting of final lining at a • distance of round 500 m behind the face (70 days) • (convergence 14-18 cm) • Long term: from pressure acting on lining after 25 years • (radial pressure 25-50 t/m2)

  10. Geotechnical parameters of rock mass • Unit weight 27 kN/m3 • Elastic modulus 15 GPa • Poisson’s ratio 0.2 • Friction angle 35/40° (lower/mean value) • Peak cohesion 3000 kPa • Residual cohesion 2000 kPa (short term) 500-750 kPa (medium term) 200-300 kPa (long term) • Plastic strain 0.5 % (for reach residual cohesion) • Dilation angle 3°

  11. Main characteristics of calc-schists • Time-dependent behaviour of rock mass (displacements) • Tendency to wedge instability on roof • Anisotropy of rock mass properties (effect of schistosity) • Reduction of rock mass strength after failure • No water circulation in the rock mass (OK for cavern stability • and thermal losses during reservoir operation)

  12. Earthquake hazard potential in EU Frejus Low hazard

  13. Type of detector to receive • Volume of excavation: • GLACIER: 160'000 m3 • LENA: 111'000 m3 • MEMPHYS: 838'000 m3 (3 caverns)

  14. LAGUNA – Largest man-made excavation  Empirical designs methods not reliable (no experience)

  15. Basic principles – Displacements • Radial displacement (δr) ~ Excavation radius (R) • Plastic radius (Rpl) ~ Excavation radius (R) δr R Rpl Road tunnel : R=6.1 m , δr=10 cm Memphys : R=33.5 m  δr=55 cm

  16. Basic principles – Effect of gravity • Wedge pressure (p) ~ Excavation radius (R) • Bolt length ~ Excavation radius (R) • Support per m2~ R2 (also for lining) p R Road tunnel : R=6.1 m , lining d=50 cm Memphys : R=33.5 m lining d=2.7 m

  17. Analysis of wedge stability

  18. Analysis of displacements - 3D model (FLAC)

  19. Displacements – Short term

  20. Failure zone – Short term

  21. GLACIER – Final lining • Thickness: 1.5 m (roof and verticalwall)

  22. LENA – Final lining • Thickness: 0.7 m • (roof and vertical wall) • In vertical walls to be installed proceeding bottom-up • Thickness of the lower part (20 m) increased to 1.2 m

  23. MEMPHYS – Final lining • Thickness: 1.5 m (roof and verticalwall), 2.3 m in the lower part (15 m)

  24. Geomechanical feasibility • GLACIER, LENA and MEMPHYS option are feasible at Fréjus site. The • overall stability of the cavern is assured. A support is however required • for wedge stability. • The geomechanical feasibility remains valid also by a small change of the • size of the excavation, both in the diameter and height of the cavern. • The geomechanical conditions at Frejus are well known and further • investigations are basically not required. The safety tunnel under • construction will provide further information. • The support system proposed guarantees the long term stability and the • absence of significant time dependent displacement of the cavity. • The support system proposed has sufficient reserve to ensure the stability • of the cavern in case of earthquake.

  25. Mechanical interaction with rock (MEMPHYS)

  26. Steel tank in contact with rock mass • The rock loads are supported by the concrete lining and will not be • transferred on the steel tank. • The water from the rock mass can cause an external load on the • imperious tank (even if apparently the rock is dry). To avoid this • type of load, it is necessary to design an external drainage system. • The earthquake is not a problem for the steel tank, if there is not an • active fault crossing the cavern (atypical situation).

  27. Thermal interaction with rock (MEMPHYS) ROCK: T = 30°C WATER: T = 13°C HEAT ENERGY TRANSFER (Q) Solution with the insulation Solution without the insulation

  28. GLACIER

  29. LENA

  30. MEMPHYS

  31. GLACIER Cost per m3(315'000 m3):~210 €/ m3

  32. LENA Cost per m3(142'000 m3):~210 €/ m3

  33. MEMPHYS Cost per m3(911'000 m3):~180 €/ m3

  34. Technical feasibility – Tank construction • Unit cost reaches 180 – 210 €/ m3; Fréjus safety tunnel: 310 €/ m3. • The solution with tank placed in contact with the rock mass is feasible at Fréjus site for LENA and MEMPHYS option. For GLACIER option an independent tank is preferable. • The solution with tank placed in contact with the rock mass can save the amount of steel needed (7‘200 kg for MEMPHYS option, 3‘600 kg for LENA option). • Both the solution with the insulation and without insulation are feasible at Fréjus site.

  35. LAGUNA-LBNO at Frejus – Option 1 Same volume as MEMPHYS option with 3 tanks but cost reductionof 11.5 M€forexcavation and support

  36. LAGUNA-LBNO at Frejus – Option 2 Excavation and supportofadditional LENA costsonly 23 M€

  37. General conclusions for Frejus • The Frejus site allows to host all the detectors options proposed within LAGUNA, i.e. GLACIER, LENA and MEMPHYS. • The rock mass behavior was deeply investigated (during highway tunnel and now safety tunnel) allowing to minimize the uncertainties and the risks related to the realization of further underground cavities. • The excellent quality of the rock, with the appropriate amount of plasticity, allows the excavation of very large cavities at a depth of 4800 m w.e., which is the deepest in Europe (for an underground laboratory). • The Fréjus safety tunnel, presently under construction, provides an optimal and completely safe access to the site during both construction and operation (whole life-time, e.g. 50 years). • The Frejus rescue team, permanently in service, ensure the highest safety support both in the tunnel and in the laboratory. • The accessibility of the Frejus site is excellent (by road or train from many international cities as Torino, Chambery, Lyon, Genève, Milano, Paris).

  38. THANKYOU FOR YOURATTENTION

  39. Graphic layout

  40. Graphic layout

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