Deep Immersed Tunnel Subjected to Fault Rupture Deformation + Strong Seismic Shaking

Transcription

1 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

2 The two components of an Earthquake Tectonic faulting Seismic shaking S, P Seismic waves hypocenter

3 The main question: Can Immersed Tunnels be Designed to withstand a sequence of: (a) a fault rupturing underneath (b) strong seismic shaking

4 Rion Antirrion Rail Link Thessaloniki Athens

5 The Rion Antirrion Straits and the Rail Link

6 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)

7 Active Faults 1 2 km Antirrion Rion

8 Βorings near Tunnel axis 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 GW S ML CH CL

9 Combination of Immersed and TBM Tunnels RION Shaft Immersed Tunnel ANTIRRION ΤΒΜ ΤΒΜ 3.2 km 1 km 3 km 9 km

10 Immersed + TBM Tunnels Embankment TBM Immersed Tunnel TBM Ground Freezing Shield-TBM Tunnel

11 Immersed Tunnel Cross-section 1.5 m 11 m 4.4 m 1.1 m 1.5 m 1.5 m 2 m m

12 Towing

13 Immersion

14 The floating tunnel segment is towed close to the previously installed bulkhead Gina profile

15 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

16 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

17 The bulkhead is removed and the omega profile is installed

18 Critical Element: the Joints Gina BEFORE CONTACT Omega Shear Key Tendon Gina AFTER CONTACT Omega Coupler

19 Major Concerns: Behaviour of Joints: (a) Decompression of Gina Rubber leading to: net tension,.. joint opening,... flooding

20 Behaviour of Joints: (b) Additional Compression leading to: Failure of Rubber in Lateral Tension

21 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

22 (a) Quasi-STATIC: Fault Rupture Imposed Deformation Tensile Opening (Decompression) Compression Fault Rupture Δ

23 (b) DYNAMIC: Seismic Shaking De-compression + Re-compression accelerations α i (t) i i + 1 α

24 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??

25 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

26 5 cm 25 cm GINA Hyperelastic Behaviour 8 Load (MN/m) (Kiyomiya 1995) Type - A Type - B Compressive Displacement (cm)

27 Immersion Joint z Immersion Joint Immersion Joint beam slider k slider c

28 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

29 (a) Dislocation Δ 3 m at bedrock level

30 Depth (m) Distance (km) Vp (m/s) 3 4 RION ANTIRRION B = 4H = 32 m 8 m Hanging wall Δ α

31 Normal Faulting on Dense Sand, α = 45ο

32 Normal Faulting on Dense Sand, α = 45 ο D/ H =.25 %

33 Normal Faulting on Dense Sand, α = 45 ο h / H =.75 %

34 Normal Faulting on Dense Sand, α = 45 ο h / H = 1. %

35 Δy (m) Position 1 Position Position β (%) Horizontal distance d (m)

36 Δx (m) Δx (m) δ x (m) Initial Hydrostatic Compression Hydrostatic Fault L = 7 m Gina: Type A δ x (m) Horizontal distance d (m) Initial Hydrostatic Compression Final Horizontal distance d (m) Hydrostatic Fault Horizontal distance d (m) Type B

37 (b) Seismic Excitation.24 g at bedrock level

38 1-D Dynamic Wave Propagation Analysis g.6.63 g a (g) g t (sec) t (sec) t (sec) 25 Profile C (hard) JMA - Kobe 1995 JMA Kobe V s (m/sec) Lefkada 23.6 Lefkada g Aegion g.3 a (g) g t (sec) t (sec) t (sec)

39 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

40 .6 15 cm.3 δ x Joint Deformation cm 1 cm t (s) 2 1 cm A B C D t (s) cm δ x cm 1 2 cm cm t (s) cm 1 16 cm t (s) 5 1 5

41 3 3 Step : Hydrostatic Compression Step 1 : Fault Rupture Step 2 : Seismic Oscillation δ x (cm) a b a b t (sec) 1

42 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 )

43 CONCLUSIONS 2. The injury of Immersed Tunnels from Fault Offset at the Baserock can be healed after strong seismic shaking

44 Thank you for your attention

45 Load (MN/m) K el b 1 b 1 a 1 a 1 K hyper Load (MN/m) K hyper Load (MN/m) Δx (cm) a b 7 7 K hyper Δx (cm)