1. General meeting LAGUNA LAGUNA – Fréjus site
Geotechnical feasability
(Rewiew of WP2 Munich January 26th-27th, 2009)
March 30th.- April 2nd 2009, Wroclaw

2. CURRENT SITUATION: GENERAL PLAN
LSM Underground Laboratory Modane
Road tunnel
Railway tunnel
Longitudinal section
>1500 m
rock overburden
6,6 km
6,2 km
12.8 km

3. Geotechnical parameters of rock mass
Unit weight kN/m3
Elastic modulus GPa
Poisson’s ratio
Friction angle 35/40° (lower/mean value)
Peak cohesion kPa
Residual cohesion kPa (short term) kPa (medium term) kPa (long term)
Plastic strain % (for reach residual cohesion)
Dilation angle 3°

4. 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)

5. Cavern design LENA 221'000 m3 GLACIER 320'000 m3 MEMPHYS 558'000 m3
21.9
17 m
41.9
19 m
47.5
110 m
D=76 m
70 m
25 m
D=67 m
D=35 m

6. Memphys – 3D model (FLAC)

7. Memphys – Displacements – Long term

8. Memphys – Failure zone – Long term

9. Memphys – Analysis of wedge stability

10. Large excavations at Frejus - Conclusions
The construction of the large excavations for the 3 detector types of Laguna is feasible at Frejus site.
For Glacier it is possible to built a unique large tank. The division into
2 smaller tanks can reduce the total construction costs of the caverns.
For Lena it is not necessary to have curved walls
The final lining should be placed at least 2-3 months after the excavation
in order to reduce the rock pressure in the long term (excavation from
top to bottom, construction of final lining from bottom to top).

11. Interaction between tank and rock mass
The stability of the rock mass during excavation is ensured by anchors and reinforced shotcrete
The definitive cavern is sustained by a concrete lining.
Glacier needs a inner, independent tank.
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 appears 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).

12. Location LAGUNA
Safety tunnel
Road tunnel
LAGUNA
Railway tunnel

13. LAYOUT (top view) Access Tunnel Safety Tunnel Road Tunnel
Control room, offices, storage, power
Safety Tunnel
Electronics
Air and water purification
Electronics
Road Tunnel
Electronics

14. LAYOUT (side view) Safety Tunnel Road Tunnel Access Tunnel
Air and water purification
Safety Tunnel
Road Tunnel
Electronics
Electronics
Control room, offices, storage, power
Access Tunnel

15. Air and water purification
LAYOUT
Access Tunnel
Safety Tunnel
Electronics
Air and water purification
Control room
Storage
Offices
Power
Electronics
Cables, piping etc
Electronics