THE REPRODUCTION ANALYSIS OF ARATOZAWA DAM DURING 2008 EARTHQUAKE

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International Symposium Qualification of dynamic

probabilistic assessment seismic hazard in Europe

Japan Dam Engineering Center THE REPRODUCTION

1 International Symposium Qualification of dynamic analyses of dams and their equipments and of probabilistic assessment seismic hazard in Europe 31th August nd September 16 Saint-Malo Nario YASUDA Japan Dam Engineering Center THE REPRODUCTION ANALYSIS OF ARATOZAWA DAM DURING 8 EARTHQUAKE Saint-Malo Yannick LE GAL

1. Main Features of Aratozawa dam Homepage of Miyagi Prefectural Government Dam type Rockfill dam with central clay core (1998) Dam height 7. m Crest length 13.7 m Crest width 1.

2 1. Main Features of Aratozawa dam Homepage of Miyagi Prefectural Government Dam type Rockfill dam with central clay core (1998) Dam height 7. m Crest length 13.7 m Crest width 1. m Slope gradients Upstream: 1:.7, Downstream: 1:.1 Design seismic coefficient.15 (dam body).18 (intake tower, bridge).16 (spillway) The reproduction analysis of Aratozawa dam during the 8 Earthquake

3 . Location of Aratozawa dam 39. Akita pref. Iwate pref. Latitude Epicenter Km Aratozawa Dam 38.8 Miyagi pref (Km) 11. Lonfitude The reproduction analysis of Aratozawa dam during the 8 Earthquake 3

4 3. Gigantic landslide by the Earthquake after Takashi IGUCHI cm of settlement at dam crest after Kyodo Press The reproduction analysis of Aratozawa dam during the 8 Earthquake

5 . Repair work of landslide 9/Oct/16 11/Apr./6 The reproduction analysis of Aratozawa dam during the 8 Earthquake 5

6 5. Earthquake monitoring (1/) (cm/s) 1 Crest (T) Max:51 Min: T, M, F -1 (cm/s) (sec) 8 Middle of core (M) Max: Min: G -5 1m 181m 155m (sec) T (cm/s) 1 M Foundation (F) Max:1 Min: m F 3m 7.17m Locations of Seismographs (sec) Earthquake Records in Stream Dir. Iwate-Miyagi Nairiku Earthquake, 8 The reproduction analysis of Aratozawa dam during the 8 Earthquake 6

7 5. Earthquake monitoring (/) Aratozawa, M.5.9,.9 Koda, 1.7 Aratozawa,.5 Max. Acc. at foundation (Stream dir., cm/sec) Acceleration amplification ratio of dam body (Crest/Foundation) The reproduction analysis of Aratozawa dam during the 8 Earthquake 7

8 6. Investigation with numerical analysis (1) Why such peculiar phenomenon occurred? () What caused the permanent deformation? Viscous Boundary Viscous Boundary Analytical Model Method for Earthquake Behavior Simulation 3-D FEM model Equivalent Linear Analysis Method for Permanent Deformation Reproduction a) Stability analysis based on circular slip surface b) Deformation calculation based on the theory of cumulative damage The reproduction analysis of Aratozawa dam during the 8 Earthquake 8

9 6-1 Procedure of numerical analysis (1) G Identification () Reproduction of earthquake motion at the bottom of model (3) Identification of reference strain and damping ratio () Simulation of the dynamic behavior in Iwate-Miyagi Nairiku earthquake (5) Calculation of permanent deformation The reproduction analysis of Aratozawa dam during the 8 Earthquake 9

6- Identification of initial shear moduli G unsaturated rock saturated rock -5 G= ρ g Vs Earthquake records Core -1-15 Depth(m) - -5-3 Eigenvalue f 1' -35 f1

10 6- Identification of initial shear moduli G unsaturated rock saturated rock -5 G= ρ g Vs Earthquake records Core Depth(m) Eigenvalue f 1' -35 f By adjusting G Vs(m/s) No f 1' = f 1 Yes G after Sawada and Takahashi (1975) The reproduction analysis of Aratozawa dam during the 8 Earthquake 1

11 Measurement of shear wave velocity Case of Miho dam 11

12 Measurement of shear wave velocity Case of Miho dam 1

13 Measurement of shear wave velocity Case of Miho dam 13

14 Measurement of shear wave velocity Case of Miho dam 1

15 Measurement of shear wave velocity Case of Shichigasyuku dam 15

16 Measurement of shear wave velocity Case of Shichigasyuku dam 16

17 6-3 Reproduction of Earthquake Motion at the Bottom of the Analytical Model Earthquake record {ff} F [T] {fw} W Vs=1m/s G=55 N/mm ρ=.6 t/m3 FAX FAY FAZ Earthquake motion at the bottom of model TXX TYX TZX = TXY TYY TZY TXZ TYZ TZZ FBX FBY FBZ The reproduction analysis of Aratozawa dam during the 8 Earthquake 17

18 6- Boundary condition (1/) First, input the earthquake wave (W) to the bottom of free field, to get the velocity response (Vf) and the displacement response (Uf) of the free field. Free field Vf Radiation damping Uf Vs=1m/s G=55 N/mm ρ=.6 t/m3 Energy inflowing (W) W is reproduced based on the earthquake record of the foundation (F) The reproduction analysis of Aratozawa dam during the 8 Earthquake 18

19 6- Boundary condition (/) Then, input the earthquake wave (W) to the bottom of foundation, and at the same time, input the responses of the free field (Vf, Uf) to the lateral boundary of the foundation, to get the responses of the whole model. Free field Radiation damping Vs=1m/s G=55 N/mm ρ=.6 t/m3 Energy inflowing(vf, Uf) Energy inflowing (W) Radiation damping The reproduction analysis of Aratozawa dam during the 8 Earthquake 19

20 6-5 Identification of reference strain and damping ratio (1/) Stream Dir. Acc.(cm/s) 1 Earthquake Response Analysis Record Max:51 Min:-55 Ana. Max:68 Min: Time(sec) 5 1 Reference strain γr 15 Frequency(Hz) By adjusting γr & hmax G 1 = G 1+ γ γ r h = h max γ γ +γ r + h E-6 1.E-5 1.E- 1.E-3 h(%) G/G Amplification Stream Dir. 1.E- Shear Strain γ The reproduction analysis of Aratozawa dam during the 8 Earthquake

21 6-5 Identification of reference strain and damping ratio (/) Category Max. damping ① Core (lower parts) % ② Core (upper part) 3% ③ Filter ④ Transition 3% ⑤ Rock (inner) ⑥ Rock (outer) 3% Reference shear strain ② ⑥ ⑥ ① ⑤ ④ ④ ⑤ ③ Identification of material properties The reproduction analysis of Aratozawa dam during the 8 Earthquake 1

22 6-6 Damping and it s nonlinearity Rayleigh type [C ]e = α [M ]e + β [K ]e 1.5 hn/h1 Here: α = f (h,ω 1 ).5 β = g (h,ω 1 ) h = h max γ γ +γ r 1 + h 1 ωn/ω1 3 Based on the frequency independency of internal damping of soil materials The reproduction analysis of Aratozawa dam during the 8 Earthquake

23 7-1 Acceleration response (1/3) Stream Direction (cm/s) 1 Crest (T) Record: Max:51 Analysis: Max:68 Min:-55 Min: (cm/s) 1 6 Middle (M) 8 Record: Max: Analysis: Max:37 1 (sec) Min:-535 Min: Record: Max:1 Foundation(F) Analysis: Max:993 (cm/s) 1 Record Analysis 1 (sec) Min:-673 Min: The reproduction analysis of Aratozawa dam during the 8 Earthquake 1 (sec) 3

24 7-1 Acceleration response (/3) Cross Stream Direction (cm/s) 1 Record Max:55 Analysis Max:61 Crest(T) Min:-37 Min: (cm/s) 1 6 Middle(M) 8 Record Max:78 Analysis Max:7 1 (sec) Min:-38 Min: Record Max:899 Foundation(F) Analysis Max:868 (cm/s) 1 Record Analysis 1 (sec) Min:-713 Min: The reproduction analysis of Aratozawa dam during the 8 Earthquake 1 (sec)

25 7-1 Acceleration response (3/3) Vertical Direction (cm/s) 1 Crest(T) Record Max:88 Analysis Max:8 Min:-6 Min: (cm/s) 1 6 Middle(M) 8 Record Max:6 Analysis Max:38 1 (sec) Min:-7 Min: Record Max:691 Foundation(F) Analysis Max:561 (cm/s) 1 Record Analysis 1 (sec) Min:-61 Min: The reproduction analysis of Aratozawa dam during the 8 Earthquake 1 (sec) 5

26 Stream Direction Fourier Spe.(cm/s) 7- Spectra & transfer functions (1/6) Crest(T) 3 1 Fourier Spe.(cm/s) Amplification 15 Foundation(F) Frequency(Hz) 15 Transfer Function Record Analysis 5 1 Frequency(Hz) 5 1 Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 15 6

27 Fourier Spec.(cm/s) Cross Stream Direction 3 Fourier Spec.(cm/s) 7- Spectra & transfer functions (/6) 3 Crest(T) 1 Foundation(F) 1 Transfer Function Record Analysis Amplification Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 7

28 Fourier Spec.(cm/s) Vertical Direction 3 Fourier Spec.(cm/s) 7- Spectra & transfer functions (3/6) 3 Crest(T) 1 Foundation(F) 1 Transfer Function Record Analysis Amplification Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 8

29 Fourier Spec.(cm/s) Stream Direction 3 Fourier Spec.(cm/s) 7-3 Spectra & transfer functions (/6) 3 Middle of core (M) Crest(T) 1 Foundation(F) 1 Transfer Function Record Analysis Amplification Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 9

30 Fourier Spec.(cm/s) Cross Stream Direction 3 Fourier Spec.(cm/s) 7-3 Spectra & transfer functions (5/6) 3 Middle of core (M) Crest(T) 1 Foundation(F) 1 Transfer Function Record Analysis Amplification Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 3

31 Fourier Spec.(cm/s) Vertical Direction 3 Fourier Spec.(cm/s) 7-3 Spectra & transfer functions (6/6) 3 MiddleCrest(T) of core (M) 1 Foundation(F) 1 Transfer Function Record Analysis Amplification Frequency(Hz) The reproduction analysis of Aratozawa dam during the 8 Earthquake 31

32 Relative Dip.(cm) 7- Comparison of relative displacement in stream direction Record Max:11.13 Analysis Max: Min: Min: Time(sec) 8 1 Record Analysis The reproduction analysis of Aratozawa dam during the 8 Earthquake 3

33 7-5 Distribution of the max. acceleration (cm/sec) (a) Cross Section (b) Axial Section The max. acceleration response of each nodal point in stream dir. occurred at different time. The reproduction analysis of Aratozawa dam during the 8 Earthquake 33

34 7-6 Distribution of the max. shear strain ( 1-) Shear strain Phenomenon Mechanical characteristics 1- Wave motion, vibration 1-1- Crack, settlement 1- Sliding, compaction, liquefaction Elastic Plastic Fracture The max. shear strain of each element occurred at different time. The reproduction analysis of Aratozawa dam during the 8 Earthquake 3

35 8. Mechanism of permanent deformation 8-1 Stability analysis based on circular slip surface 3 Sliding dir. 6 5 Upstream side Arc No. Safety Factor Sliding Disp.(cm) Downstream side The reproduction analysis of Aratozawa dam during the 8 Earthquake 35

36 8- Deformation calculation based on the theory of cumulative damage.6 cm 6.81 cm Deformation after the earthquake Ur = Ua -Ub The reproduction analysis of Aratozawa dam during the 8 Earthquake 36

8-3 Distribution of the max. shear strain Elevation(m) 75 Differential settlement gage Guide pipe popped out cm. (After Shimamoto, et al. 8) 65 55 5 35 5 Calculation 15 Measurement 5-3. -. -1.

37 8-3 Distribution of the max. shear strain Elevation(m) 75 Differential settlement gage Guide pipe popped out cm. (After Shimamoto, et al. 8) Calculation 15 Measurement Extension(%) Compression(%) Comparison of measured and calculated subsidence strain (Measurement period: Dec., 7 to June 17, 8) The reproduction analysis of Aratozawa dam during the 8 Earthquake 37

38 9. CONCLUSIONS Mechanism of the peculiar seismic behavior Large shear strain occurred near the rock contact surface, which reduced the stiffness and increased the damping of the embankment. The material near the crest and the slope surface became loosely during the earthquake, hence, the high frequency components lost. Mechanism of permanent deformation Permanent deformation was mainly due to the shaking subsidence of the soil materials. Sliding phenomenon did not occur during the earthquake. The reproduction analysis of Aratozawa dam during the 8 Earthquake 38

39 Title 16 THANK YOU FOR YOUR ATTENTION 39

A STUDY ON EARTHQUAKE RESPONSES OF ACTUAL ROCK-FILL DAM AND NUMERICAL ANALYSES

A STUDY ON EARTHQUAKE RESPONSES OF ACTUAL ROCK-FILL DAM AND NUMERICAL ANALYSES 145 Hiroshi SATO 1 And Yasuyoshi OBUCHI 2 SUMMARY In order to assess the safety of rock-fill dams during earthquakes, the