Nickolas Ambraseys Memorial Symposium Deep Immersed Tunnel Subjected to Fault Rupture Deformation + Strong Seismic Shaking George Gazetas, N.T. Univ. of Athens Ioannis Anastasopoulos, Univ. of Dundee Rallis Kourkoulis, N.T. Univ. of Athens
The two components of an Earthquake Tectonic faulting Seismic shaking S, P Seismic waves hypocenter
The main question: Can Immersed Tunnels be Designed to withstand a sequence of: (a) a fault rupturing underneath (b) strong seismic shaking
Rion Antirrion Rail Link Thessaloniki Athens
The Rion Antirrion Straits and the Rail Link
UNDER-SEA RAILWAY LINK Difficult + Pioneering Project --------------------------------------------------- Great Water Depths: 65 7 m for a total length of > 1 km Very High Seismicity ( PGA >.5 g ) Soft Soils to large depths (> 6 m)
Active Faults 1 2 km Antirrion Rion
Βorings near Tunnel axis 2 4 6 8 1 12 14 Depth (m) RION B7 B14 B12 C1 B2 C2 B9 D1 B3 C3 B11 B4 C4 B6 C5 B1 B17 B1 P4 P3 P2 P1 B8 B13 B5 ANTIRRION 2 4 6 8 1 12 14 GW S ML CH CL
Combination of Immersed and TBM Tunnels RION Shaft Immersed Tunnel ANTIRRION ΤΒΜ ΤΒΜ 3.2 km 1 km 3 km 9 km
Immersed + TBM Tunnels Embankment TBM Immersed Tunnel TBM Ground Freezing Shield-TBM Tunnel
Immersed Tunnel Cross-section 1.5 m 11 m 4.4 m 1.1 m 1.5 m 1.5 m 2 m 1 3 23 m
Towing
Immersion
The floating tunnel segment is towed close to the previously installed bulkhead Gina profile
The tunnel segment is filled with water (or other type of ballast) and immersed The hydrostatic pressures acting on the two bulkheads are equal The Gina profile is not yet compressed
The water between the two bulkheads is pumped out The hydrostatic pressure is now acting only on the left bulkhead The Gina profile is compressed
The bulkhead is removed and the omega profile is installed
Critical Element: the Joints Gina BEFORE CONTACT Omega Shear Key Tendon Gina AFTER CONTACT Omega Coupler
Major Concerns: Behaviour of Joints: (a) Decompression of Gina Rubber leading to: net tension,.. joint opening,... flooding
Behaviour of Joints: (b) Additional Compression leading to: Failure of Rubber in Lateral Tension
2 Types of Seismic Loading in the life of the tunnel : (a) Quasi-STATIC: Fault Rupture Underneath, Imposes Deformation on the Surface (b) DYNAMIC: Seismic Shaking from Waves Propagating through Soil
(a) Quasi-STATIC: Fault Rupture Imposed Deformation Tensile Opening (Decompression) Compression Fault Rupture Δ
(b) DYNAMIC: Seismic Shaking De-compression + Re-compression accelerations α i (t) i i + 1 α
The two loading situations from two different seismic events which may occur many years apart The Question is: How will the injured tunnel from the fault rupture behave during a very strong seismic shaking??
DESIGN SITUATIONS : ------------------------------------------------------ (a) Dislocation Δ 3 m at bedrock level (b) selected time histories from world-wide records with strong directivity effects (Kobe, Aegion, Rinaldi, Lefkada, ) all scaled to PGA.24 g at bedrock level
5 cm 25 cm GINA Hyperelastic Behaviour 8 Load (MN/m) 6 4 2 (Kiyomiya 1995) Type - A Type - B 1 2 3 4 Compressive Displacement (cm)
Immersion Joint z Immersion Joint Immersion Joint beam slider k slider c
segment F y F x Gina Immersion Joint beam Immersion Joint F y Passive Failure F y Δx slider k slider c Δy F x a Shear Key Allowance Δy + Friction μ x Δx t t t x i-1 /C α x i /C α Asynchronous Seismic Shaking x i+1 /C α
(a) Dislocation Δ 3 m at bedrock level
Depth (m) Distance (km) - 4 2 3-2 2 4 1 2 4 5 Vp (m/s) 3 4 RION ANTIRRION B = 4H = 32 m 8 m Hanging wall Δ α
Normal Faulting on Dense Sand, α = 45ο
Normal Faulting on Dense Sand, α = 45 ο D/ H =.25 %
Normal Faulting on Dense Sand, α = 45 ο h / H =.75 %
Normal Faulting on Dense Sand, α = 45 ο h / H = 1. %
-.6 5 1 -.6 5 1 -.6 5 1 -.6 5 1 Δy (m) -.5-1.5-2 -2.5-16 -12-8 -4 4 8 12 16-1.6 -.6 5 1.6 -.6 5 1.6 -.6 5 1 Position 1 Position 1.6 -.6 5 1.6.6.6.6.4 Position 1 -.6 -.6 -.6 5 1 5 1 -.6 5 1 5 1 β.3.2.6 -.6 5 1.6 -.6 5 1.6 -.6 5 1.6 -.6 5 1 (%).1 -.1-16 -12-8 -4 4 8 12 16 Horizontal distance d (m)
Δx (m) Δx (m) δ x (m) 4 3 2 1 Initial Hydrostatic Compression Hydrostatic Fault L = 7 m Gina: Type A δ x (m) 4 3 2 1 2 4 6 8 1 2 4 6 8 1 Horizontal distance d (m) Initial Hydrostatic Compression Final 2 4 6 8 1 Horizontal distance d (m) Hydrostatic Fault 2 4 6 8 1 Horizontal distance d (m) Type B
(b) Seismic Excitation.24 g at bedrock level
1-D Dynamic Wave Propagation Analysis.6.6.5 g.6.63 g.3.3.3 a (g) -.3 -.6.48 g 5 1 15 t (sec) -.3 -.6 5 1 15 t (sec) -.3 -.6 5 1 15 t (sec) 25 Profile C (hard) 1 13.6.3 JMA - Kobe 1995 JMA Kobe 1995.6.3 25 5 75 1 125 V s (m/sec) Lefkada 23.6 Lefkada 23.24 g Aegion 1995.24 g.3 a (g) -.3 -.6.24 g 5 1 15 t (sec) -.3 -.6 5 1 15 t (sec) -.3 -.6 5 1 15 t (sec)
Application of Seismic Base Excitation l a x a x i a x j a l t t t t EC8 x i /C α x j /C α l /C α C α : apparent wave velocity Time lag t i = x i /C α
.6 15 cm.3 δ x -.3 -.6 3 2 1 3 2 1 5 1 Joint Deformation.6.3 -.3.6.3 5 cm 1 cm -.3 5 5 1 1 t (s) 2 1 cm 1 3 2 1 -.6 -.6 -.6 5 5 1 1 5 1 5 1 5 1 A B C D.6.3 -.3 t (s) 3 2 2 1 7 cm 1 5 3 3 3 3.6 2 2.6 2.6 2.6 δ x.3 -.3 1 1 1 1.3 -.3 1 4 cm 1 2 cm 5 -.6 5 5 5 1 1.5 cm 5 15 5 1 1 t (s).3 1.3 8 cm 1 16 cm -.3 -.3 5 -.6 -.6 -.6 5 1 5 1 5 1 1 5 1 t (s) 5 1 5
3 3 Step : Hydrostatic Compression Step 1 : Fault Rupture Step 2 : Seismic Oscillation 1 2 3 5 7 9 11 δ x (cm) 25 25 2 2 a 1 1 7 1 2 3 11 b 1 15 15 1 1 a 7 9 7 b 7 5 5-6 -4-2 2 4 6 8 1 2 4 6 8 t (sec) 1
CONCLUSIONS 1. Immersed Tunnels: Capable of Withstanding Significant Fault + Dynamic Deformations PREREQUISITE: (a) Special Gina Profiles (e.g., h = 5 cm) (b) Small Length of Segments (e.g., L = 7 m )
CONCLUSIONS 2. The injury of Immersed Tunnels from Fault Offset at the Baserock can be healed after strong seismic shaking
Thank you for your attention
Load (MN/m) 8 6 4 2 1 K el b 1 b 1 a 1 a 1 K hyper Load (MN/m) 8 6 4 2 7 K hyper Load (MN/m) 8 6 4 2 7 1 2 3 4 Δx (cm) a b 7 7 K hyper 4 1 2 3 4 Δx (cm)