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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 CURRENT SITUATION: GENERAL PLAN LSM Underground Laboratory Modane G4 Centrale C Usine C Railway tunnel LAGUNA Fréjus Site Longitudinal section >1500 m rock overburden 6,6 km 6,2 km 12.8 km 12.8 68 km G5 PHT 17 PHT 15 G3 (LSM) PHT 11 C en G 2 tr Usin ale B eB PHT 9 PH T5 PHT 3 Road tunnel G1 LAGUNA Fréjus Site Geotechnical parameters of rock mass • Unit weight 27 kN/m3 • Elastic modulus 15 GPa • Poisson’s ratio 0.2 • Friction angle 35/40° • 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° (lower/mean value) 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) LAGUNA Fréjus Site • Reduction of rock mass strength after failure • No water circulation in the rock mass (OK for cavern stability and thermal losses during reservoir operation) Cavern design GLACIER 320'000 m3 MEMPHYS 558'000 m3 41.9 D=67 m 70 m D=76 m 19 m 47.5 25 m D=35 m 110 m LAGUNA Fréjus Site 21.9 17 m 9m LENA 221'000 m3 LAGUNA Fréjus Site Memphys – 3D model (FLAC) LAGUNA Fréjus Site Memphys – Displacements – Long term LAGUNA Fréjus Site Memphys – Failure zone – Long term LAGUNA Fréjus Site Memphys – Analysis of wedge stability 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 LAGUNA Fréjus Site • 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). 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. LAGUNA Fréjus Site •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). Location LAGUNA Safety tunnel LAGUNA Fréjus Site Road tunnel LAGUNA Railway tunnel LAYOUT (top view) Access Tunnel Electronics Safety Tunnel Electronics Electronics Road Tunnel LAGUNA Fréjus Site Air and water purification Control room, offices, storage, power LAYOUT (side view) Road Tunnel Air and water purification Safety Tunnel Electronics LAGUNA Fréjus Site Access Tunnel Control room, offices, storage, power Electronics LAYOUT Safety Tunnel Air and water purification Control room Electronics Electronics Storage LAGUNA Fréjus Site Electronics