general meeting laguna laguna – fréjus site geotechnical feasability (rewiew of wp2 munich...
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General meeting LAGUNA
LAGUNA – Fréjus site
Geotechnical feasability
(Rewiew of WP2 Munich January 26th-27th, 2009)
March 30th.- April 2nd 2009, Wroclaw
LA
GU
NA
Fré
jus
Sit
e
>1500 m
rock overburden
km 1
2.86
8
PH
T 3
PH
T 5
Centrale B
PH
T 9
(LSM)
G1
G2
PH
T 1
7
PH
T 1
5
PH
T 1
1
G5
G3 Centrale CG4
Usine BUsine C
LSM Underground Laboratory Modane
Railway tunnel
CURRENT SITUATION: GENERAL PLAN
Longitudinal section
6,2 km
12.8 km
6,6 km
Road tunnel
LA
GU
NA
Fré
jus
Sit
e
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°
LA
GU
NA
Fré
jus
Sit
e
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)
LA
GU
NA
Fré
jus
Sit
e
Cavern design
11
0 m
25
m 70
m1
7 m
19
m
9 m
41.9
D=67 mD=76
m
21.9
47.5
LENA221'000 m3
GLACIER320'000 m3
MEMPHYS558'000 m3
D=35 m
LA
GU
NA
Fré
jus
Sit
e
Memphys – 3D model (FLAC)
LA
GU
NA
Fré
jus
Sit
e
Memphys – Displacements – Long term
LA
GU
NA
Fré
jus
Sit
e
Memphys – Failure zone – Long term
LA
GU
NA
Fré
jus
Sit
e
Memphys – Analysis of wedge stability
LA
GU
NA
Fré
jus
Sit
e
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).
LA
GU
NA
Fré
jus
Sit
e
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).
LA
GU
NA
Fré
jus
Sit
e
Railway tunnel
LAGUNA
Road tunnel
Safety tunnel
Location LAGUNA
LA
GU
NA
Fré
jus
Sit
e
LAYOUT (top view)
Control room,
offices, storage, power
Air and water
purification
Roa
d T
unne
l
Safety Tunnel
Access Tunnel
Electronics
Electronics
Electronics
LA
GU
NA
Fré
jus
Sit
e
LAYOUT (side view)
Road TunnelSafety Tunnel
Access Tunnel
Air and water
purification
Control room,
offices, storage, power
Electronics Electronics
LA
GU
NA
Fré
jus
Sit
eLAYOUT
Control room
Air and water
purification
Ac c
ess
Tun
nel
Cables, piping etc
Pow
er
Offi
ces
Sto
rage
Electronics
Electronics
Electronics
Safety Tunnel