IN SITU SOIL PROPERTIES FOR SEISMIC SITE RESPONSE · 2019. 11. 20. · dynamic analyses of...

IN SITU SOIL PROPERTIES FOR SEISMIC SITE RESPONSE

Takaji KokushoProfessor, Dr. of Eng., Registered Eng.

Chuo University, Tokyo

Major References for presentation(1/2):

Aoyagi, T. (2000): Inversion analysis for soil properties based on vertical array record using the extended Bayesian method, Master’s thesis, Graduate school of Chuo University.

Fukushima, Y. and Midorikawa, S.(1994): Evaluation of site amplification factors based on average characteristics of frequency dependent Q-1 of sedimentary strata, J. Struct. Constr. Eng. Architectural Institute of Japan, No.460, 37-46, 1994.

Iwasaki, and Tatsuoka, F. (1978): Shear moduli of sands under cyclic torsional shear loading, Soils and Foundations, Vol.18, No.1, 39-56.

Kokusho, T. (1980): Cyclic triaxial test of dynamic soil properties for wide strain range. Soils and Foundations: Vol.20, No.2, 45-60.

Kokusho, T. (1982): Dynamic soil properties and nonlinear seismic response of ground, PhD Dissertation presented to Tokyo University (in Japanese)

Kokusho,T., Yoshida,Y. and Esashi,Y. (1982): Dynamic soil properties of soft clay for wide strainrange. Soils and Foundations: Vol.22, No.4, 1-18.

Kokusho,T. and Tanaka,Y. (1994): Dynamic properties of gravel layers investigated by in-situ freezing sampling. Geotechnical Special Publication No44 -Ground Failures under Seismic Conditions, ASCE Convention (Atlanta), 121-140.

Major References for presentation(2/2):

Kokusho, T. Sato, K. and Matsumoto, M. (1996): Nonlinear dynamic soil properties back-calculated from strong motions during Hyogoken-Nambu Earthquake. Proc. 11th World Conference on Earthquake Engineering, Acapulco, CD publication.

Kokusho, T. & Matsumoto, M. (1998): Nonlinearity in site amplification and soil properties during the 1995 Hyogoken-Nambu earthquake. Special Issue on Geotechnical Aspects of the January 17, 1995Hyogoken-Nambu Earthquake, No.2; Soils and Foundations: 1-10.

Kokusho, T. and Aoyagi, T. (2001): Insitu nonlinear soil properties back-calculated from vertical array records of 1995 Kobe earthquake, Proc. International Conference on In Situ Measurement of Soil Properties and Case Histories, Indonesian Geotechnical Society, Bali, 473-480.

Kokusho, T. and Mantani, (2002):. Seismic amplification evaluation in a very deep down hole array site, 12th European Conference on Earthquake Engineering, Paper Reference 797.Nuclear Power Engineering Corporation(2001): Study of Evaluation Methods for Seismic Wave Propagation Characteristics, Report of Siting Reliability Studies relating to seismic design for nuclear power plants (in Japanese).

Seed, H. B., Wong, R. T., Idriss, I. M. and Tokimatsu, K. (1986): Moduli and damping factors for dynamic analyses of cohesionless soils, Journal of Geotechnical Engineering, Vol.112, No.11, 1016-1032.

Suetomi, I. (1997): A Program manual for optimization of soil structure by Bayes Method. Central Research Institute of Sato Kogyo Com. Ltd, (in Japanese).

UNSOLVED PROBLEMS FOR SEISMIC SITE RESPONSE

1. In situ modulus degradation compared with laboratory tests.

2. In situ damping compared with laboratory tests.

3. Combination of strain-dependency effect and pore pressure-buildup effect on degradation for larger strains.

4. Amplification in vertical motions and related soil properties.

5. Amplification in deep ground and related soil properties; Effect of confining stress-dependency and frequency dependency of damping.

Topics of the presentation:

Seismic site amplification during strong earthquakes based on vertical

array recordsBack-calculated in situ soil properties

versus lab dataSoil properties for deep soil response

Locations of 4 vertical array sites around Kobe City

0 500 1000 1500 2000 2500

0

20

40

60

80

100

Vp-initialVs-initialN-value

Vp, Vs by PS-logging (m/s)

0 50 100 150 200 2SPT N-value

Dep

th (m

)

WLGL-0m

GL-16.4m

GL-32.4m

GL-83.4m

PI

GL-4.0S/G

CHS

G/S

G

CH

G

Seismograph

0 1000 2000 3000 4000

0

20

40

60

80

100



Dep

th (m

)

0 100 200 300 40SPT N-value

C

SF

G

M

SM WL

SF

SF

M/G

M

Rock

KNK

GL-2.0

GL-0m

GL-25m

GL-100m

Seimograph

0 1000 2000 3000

0

20

40

60

80

100



Dep

th (m

)

0 50 100 150 200 250 300 3SPT N-value

SM

M

G

GS

CH

G

M

TKSWL

GL-2.5G

GL-0m

GL-25m

GL-100m

Seismogragh

0 500 1000 1500 2000 2500 3000 3500

0

20

40

60

80

100



Dep

th (m

)

SPT N-value

SMMGSC

G

CHSFCH

CH

CH

CH

WL

SGK

GL-2.0

0 50 100 150 200 250 300 35GL-0m

GL-25m

GL-97m

Seimograph

Soil profiles, Vp, Vs, SPT-N & Seismometer installation levels in 4 vertical array sites

-100

-80

-60

-40

-20

0

0 100 200 300 400 500 600 700 800 900 1000

A cceleration(gal)

EW (PI) N S U D EW (K N K ) N S U D EW (TK S) N S U D EW (SG K ) N S U DD

epth(m

)

Max. Acc. in 4 vertical array sites during Kobe EQ

Vs-ratio (base to surface) versus amplification ratio of maximum acceleration

0 2 4 6 8 10 120

2

4

6

8

10

12

本震直後の余震

)(

Shima(1978)

1.0

0.33

PI MS PI AS(前震) PI AS(余震) KNK MS KNK AS SGK MS SGK AS TKS MS TKS AS

Surface Acc/Base Acc

Vs ratio: Base/Surface

F.SA.S

AS immediatelyafter MS

Max. Base Acc. versus Acc. amplification (Surf./Base)

1 10 100 10000

2

4

6

8

10

本震直後の余震

)(

PI M S PI A S(前震) PI A S(余震) K N K M S K N K A S TK S M S TK S A S SG K M S SG K A S

Surface Acc/Base Acc

B ase A cc (gal)

F.SA.SAS immediately

after MS

0.01 0.1 1 10 1000

2

4

6

8

10

PI M S PI A S(前震) PI A S(余震) K N K M S K N K A S TK S M S TK S A S SG K M S SG K A S 回帰直線

Surface Vel/Base Vel

B ase V el (kine)

Max. Base Vel. versus Max. Vel. Amplification (Surf./Base)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10( After Shock : before Main Shock

PI EW-direction GL-0m/GL-83.4m

Average

94 06281308

94 07281001

94 10241151

94 11092026

94 11100038

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8


PI NS-direction GL-0m/GL-83.4m

Average

94 06281308 94 07281001

94 10241151

94 11092026 94 11100038

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8

10


PI UD-direction GL-0m/GL-83.4m

Average

94 06281308

94 07281001 94 10241151

94 11092026 94 11100038

Spectrum ratio

Frequency (Hz)

NS EW

UD

Spectrum ratio

(PI: small shocks before main shock)

Comparison of averaged spectrum

ratios of small shocks before & after main

shock (PI)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8


berore AfterShock First.peak Amp= 4.74 Freq= 0.78(Hz)after AfterShock First.peak Amp= 4.54 Freq= 0.78(Hz)

before AfterShock Average

after AfterShock Average

Spectrum ratio

Frequency (Hz)0 1 2 3 4 5 6 7 8 9 10

0

2

4

6

8


berore AfterShock First.peak Amp= 3.19 Freq= 0.83(Hz)after AfterShock First.peak Amp= 3.57 Freq= 0.88(Hz)



Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8




Spectrum ratio

Frequency (Hz)

NS

UD

EWBefore

After

Before

After

Before

After

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

SGK EW-direction GL-0m/GL-97m

Average

01170738

01170858

01171305

01152316

02182315

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

SGK NS-direction GL-0m/GL-97m

Average

01170738

01170858

01171305 01152316

02182315

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8

SGK UD-direction GL-0m/GL-97m

Average

01170738

01170858

01171305

01152316

02182315Spectrum ratio

Frequency (Hz)

NS EW

UD

Spectrum ratio

(SGK: aftershocks)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

TKS EW-direction GL-0m/GL-100m

Average

01170628

01170642

01170738

02182137

Spectrum ratio

Frequency (Hz)0 1 2 3 4 5 6 7 8 9 10

0

2

4

6

8

10

TKS NS-direction GL-0m/GL-100m

Average

01170628

01170642

01170738

02182137

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8

10

TKS UD-direction GL-0m/GL-100m

Average

01170628

01170642

01170738

02182137

Spectrum ratio

Frequency (Hz)

NS EW

UD

Spectrum ratio

(TKS: aftershocks)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

KNK EW-direction GL-0m/GL-100m

Average

01170550

01170553

01170629

01170858

01200047

01230243

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

40

50

KNK NS-direction GL-0m/GL-100m

Average

01170550

01170553

01170629

01170858

01200047

01230243

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

20

40

60

80

KNK UD-direction GL-0m/GL-100m

Average

01170550

01170553

01170629

01170858

01200047

01230243Spectrum ratio

Frequency (Hz)

NS EW

UD

Spectrum ratio

(KNK: aftershocks)

0 1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

6

7

8

9

10(AfterShock : before MainShock)


Main Shock First.peak Amp= 2.91 Freq= 0.83(Hz)After Shock First.peak Amp= 4.74 Freq= 0.78(Hz)

MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

6

7




MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8

10



MainShock AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

NS EW

UDComparison of spectrum ratio of small shocks and

main shock (PI)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

SGK EW-direction GL-0m/GL-97m


MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

SGK NS-direction GL-0m/GL-97m


MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

SGK UD-direction GL-0m/GL-97m

MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

NS EW

UDComparison of averaged spectrum ratio of

aftershocks and main shock (SGK)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

TKS EW-direction GL-0m/GL-100m

Main Shock First.peak Amp=10.96 Freq= 1.12(Hz)After Shock First.peak Amp= 5.83 Freq= 1.22(Hz)

MainShock

AfterShock Average Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

TKS NS-direction GL-0m/GL-100m


MainShock AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

2

4

6

8

TKS UD-direction GL-0m/GL-100m

MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

NS EW


aftershocks and main shock (TKS)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

KNK EW-direction GL-0m/GL-100m

Main Shock First.peak Amp=18.81 Freq= 1.12(Hz)After Shock First.peak Amp=16.34 Freq= 1.12(Hz)

MainShock

AfterShock Average

Average+SD Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

KNK NS-direction GL-0m/GL-100m

Main Shock First.peak Amp=18.52 Freq= 1.03(Hz)After Shock First.peak Amp=15.65 Freq= 1.07(Hz)

MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

10

20

30

40

50

KNK UD-direction GL-0m/GL-100m

MainShock

AfterShock Average

Average+SD

Average-SD

Spectrum ratio

Frequency (Hz)

NS EW


aftershocks and main shock (KNK)

0 5 10 15 20-200

-100

0

100

200

U D

Acceleration(gal)

Tim e(sec)

-800

-400

0

400

800

analysis dom ain

a part of P-waveskip dataAcceleration(gal)

EW

Analysis of vertical motion for initial P-wave

0 2 4 6 8 10 12 14 16 18 200

5

10

15

20

25PI　UD-direction　-0m /-83.4m

Spectrum ratio

Frequency(Hz)

M ainShock94 6/28 13:0894 7/28 10:0194 10/24 11:5194 11/09 20:2694 11/10 00:38

0 2 4 6 8 10 12 14 16 18 200

5

10

15SG K　UD-direction　-0m /-97m

M ain Shock 95 1/17 07:38 95 1/17 08:58 95 1/17 13:05 95 1/25 23:16 95 2/18 23:15

Spe

ctrum ratio

Frequency(Hz)

Comparison of spectrum ratios of vertical motion

for initial P-wave between main shock and

aftershocks

0 2 4 6 8 10 12 14 16 18 200

5

10

15

TKS UD -direction 0/100

M ain Shock 1170628 1170642 1170738 2182137

Spectrum ratio

Frequency(H z)

0 2 4 6 8 10 12 14 16 18 200

5

10

15

20

25

30

KNK UD-direction 0/100

M ain Shock 1170550 1170553 1170629 1170858

Spectrum ratio

Frequency(Hz)

Comparison of spectrum ratios of vertical motion

for initial P-wave between main shock and

aftershocks

1 10 100 10000

10

20

30

40

PI Main PI After SGK Main SGK After TKS Main TKS After KNK Main KNK After

Maximum Spectrum ratio

Acceleration at Base Layer (gal)

1 10 100 10000

4

8

12


Average Spectrum ratio (0.5Hz-2.5Hz)


Average values (0.5-2.5Hz)

Peak values

Base Acc. versus Spectrum Ratios of horizontal motions

(Peak & Average values)

1 10 100 10000

10

20

50

60

70

80


Maximum Spectrum ratio


1 10 100 10000

1

2

3

4

5

6

7

8

PI Main PI After SGK MainSGK After

TKS MainTKS After

KNK MainKNK After

Average Spectrum ratio (2.0Hz-8.0Hz)


Base Acc. versus Spectrum Ratios of vertical motions (Peak & Average values)

Average values (0.5-2.5Hz)

Peak values

SUMMARY ON SITE AMPLIFICATION BASED ON VERTICAL ARRAY RECORDS

•Clear Acc. amplification reduction for increasing base Acc. The same trend for Vel. though milder.

•Steady spectral response for small shocks.

•Reduction in peak frequencies and magnitudes of spectrum ratios between main shocks and small shocks particularly in liquefaction sites．

•Increase in amplification with increasing Vs ratio between base and surface.　　　

•In vertical motions, no difference in peak frequenciesbetween main shocks and small shocks

How to back-calculate in situ properties from vertical array records

Optimize Vs (S-wave velocity) and D (damping ratio) based on 1D Multiple Reflection Theory of SH-wave.

Minimize residuals by EBM between observed and computed spectrum ratios.

Main shock properties compared with small shock linear properties for in situ degradation curves.

Identify in situ soil-specific properties.

0 1 2 3 4 5 6 7 8 9 100

5

10

15

PI EW -direction G L-0m /G L-83.4m (A fter Shock) (inversion result)

O BSERV ED A V ERA G E SPEC TRU M RA TIO A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED

Amplification Factor

Frequency(H z)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

PI N S-direction G L-0m /G L-83.4m (A fter Shock) (inversion result)

O BSERV ED A V ERA G E SPEC TRU M RA TIO

A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED


Frequency(H z)

Comparison of inversion and observation

(Small shocks before main shock: PI)

NS

EW

0 1 2 3 4 5 6 7 8 9 100

5

10

SG K EW -direction G L-0m /G L-97m (A fter Shock) (inversion result)


A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED


Frequency(H z)

0 1 2 3 4 5 6 7 8 9 100

5

10

SG K N S-direction G L-0m /G L-97m (A fter Shock) (inversion result)


A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED


Frequency(H z)

NS

EW


(Aftershocks:SGK)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

TK S EW -direction G L-0m /G L-100m (A fter Shock) (inversion result)


A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED


Frequency(H z)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

TK S N S-direction G L-0m /G L-100m (A fter Shock) (inversion result)


A V ERA G E+SD

A V ERA G E-SD

O PTIM IZED


Frequency(H z)

NS

EW


(Aftershocks:TKS)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

40

KNK NS-direction GL-0m/GL-100m (After Shock) (inversion result)

OBSERVED AVERAGE SPECTRUM RATIO

AVERAGE+SD

AVERAGE-SD

OPTIMIZED


Frequency(Hz)

0 1 2 3 4 5 6 7 8 9 100

10

20

30

KNK EW-direction GL-0m/GL-100m (After Shock) (inversion result)

OBSERVED AVERAGE SPECTRUM RATIO

AVERAGE+SD

AVERAGE-SD

OPTIMIZED


Frequency(Hz)

NS

EW


(Aftershocks:KNK)

0 1 2 3 4 5 6 7 8 9 100

1

2

3

4

P I N S-direction G L -0m /G L -83.4m (M ain Shock) (inversion result)

O B SE R V E D SP E C T R U M R A T IO O P T IM IZ E D

電研


F requency(H z)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

SG K N S-direction G L -0m /G L -97m (M ain Shock) (inversion result)

O B SE R V E D SP E C T R U M R A T IO

O P T IM IZ E D

電研


F requency(H z)

PI NS

SGKNS

Comparison of inversion and observation (Main

shock: PI & SGK) Horizontal

0 1 2 3 4 5 6 7 8 9 100

4

8

12

T K S N S-direction G L -0m /G L -100m (M ain Shock) (inversion result)

O B SE R V E D SP E C T R U M R A T IO O P T IM IZ E D

電研


F requency(H z)

0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

K N K N S-direction G L -0m /G L -100m (M ain Shock) (inversion result)

O B SE R V E D SP E C T R U M R A T IO

O P T IM IZ E D

電研Amplification Factor

F requency(H z)

TKSNS

KNKNS

Comparison of inversion and observation (Main shock: TKS & KNK)

-80

-60

-40

-20

0

0 100 200 300 400 500

-80

-60

-40

-20

00 100 200 300 400 500

INITIAL OPTIMIZED AS EW OPTIMIZED AS NS OPTIMIZED MS EW OPTIMIZED MS NS Water table GL-4.0m

Shear wave velocity : Vs (m/s)

Depth from G

L (m)

-100

-80

-60

-40

-20

0

0 100 200 300 400 500 600-100

-80

-60

-40

-20

00 100 200 300 400 500 600

Shear wave velocity : V s (m /s)

Depth from G

L (m)

IN ITIA L O PTIM IZED A S EW O PTIM IZED A S N S

O PTIM IZED M S EW O PTIM IZED M S N S W ater table G L-2m

PI

SGK

Optimized Vs distribution along depth for MS & AS

compared with wave-logging (PI & SGK)

-100

-80

-60

-40

-20

0

0 100 200 300 400 500 600 700-100

-80

-60

-40

-20

00 100 200 300 400 500 600 700

Shear wave velocity : Vs (m /s)

Depth from G

L (m)

INITIAL

O PTIM IZED AS EW O PTIM IZED AS NS

O PTIM IZED M S EW O PTIM IZED M S NS

W ater table G L-2m

-100

-80

-60

-40

-20

0

0 200 400 600 8001000120014001600-100

-80

-60

-40

-20

00 200 400 600 8001000120014001600

Shear wave velocity : Vs (m/s)

Depth from G

L (m)

INITIAL OPTIMIZED AS EW OPTIMIZED AS NS OPTIMIZED MS EW OPTIMIZED MS NS Water table GL-2.2m

TKS

KNK

Optimized Vs distribution along depth for MS & AS

compared with wave-logging (TKS & KNK)

0 500 1000 1500 2000 2500

0

20

40

60

80

100

ＰＳ検層

本震同定

Ｐ波速度 Vp (m/s)

深度 (m)

地下水位埋立土

軟弱粘土

砂

GL 0

GL-16.4

GL-32.4

GL-83.4m

洪積礫

(t=0~5.12ｓのみを解析）

Comparison of inversion and observation (Main shock: PI ) Vertical

Wave logging

Optimized for Main shockt=0~5.1 s for intial P-wave

P-wave velocity: Vp (m/s)

Dep

th (

m)

Water tableFill

Soft clay

Sand

Gravel

0 2 4 6 8 100

4

8

12

(b) G L.0m /G L-97m

Spectrum ratio

Frequency(Hz)

0

4

8

12

16SG K Aftershock-A (NS)

(a) G L.0m /G L-24.9m

Spectrum ratio

0 2 4 6 8 100

4

8(b) G L.0m /-97m

Spe

ctrum ratio

Frequency (Hz)

M easured Initial guess Back-calculated L.M .S.M .

0

4

8SG K M ain shock (NS)

(a) G L.0m /-29.4m

Spe

ctrum ratio

0 2 4 6 8 100

4

8

12

(b) G L.0m /G L-97m

Spe

ctrum ratio

Frequency(Hz)

0

4

8

12

16 SG K Aftershock-C (NS)

(a) G L.0m /G L-24.9m

Spectrum ratio

M easured Initial guess Back-calculated

0 2 4 6 8 100

4

8

12

(b) G L.0m /G L-97m

Spectrum ratio

Frequency (Hz)

0 2 4 6 8 100

4

8

12

16 SG K Aftershock-B (NS)

(a) G L.0m /G L-24.9m

Spe

ctrum ratio

Measured & Back-calculated spectrum ratios compared in SGK for Aftershocks C, B, A and Main Shock

AS-C AS-B

AS-A MS

-100

-80

-60

-40

-20

00 4 8 12 16 20

(b) Dam ping ratio (%)

M S(EW ) M S(NS) AS-A(EW ) AS-A(NS) AS-B(EW ) AS-B(NS) AS-C(EW ) AS-C(NS)

-100

-80

-60

-40

-20

00 200 400 600

S-wave logging

(a) S-wave velocity Vs (m /s)

Depth (m)

Back-calculated S-wave velocity and Damping in SGK for Aftershocks and Main Shock

( )20 MS ASG G Vs Vs=

5 6 7 8 9 1 0 1 1- 4 0

- 2 0

0

2 0

4 0

(a ) S G K A S - B N S - d ire c tio n

T im e (s )

In p u t W a v e

- 4 0

- 2 0

0

2 0

4 0

GL-24.9m

GL-97m

Acceleration(cm/s

2 ) - 4 0- 2 0

0

2 0

4 0

GL-0m

O b s e rv e d C a lc u la te d

1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0- 5 0 0

- 2 5 0

0

2 5 0

5 0 0

(b ) S G K M S N S - d ire c tio n

G L - 9 7 m

Acceleration(cm/s2)

In p u t W a v e

T im e (s )

- 5 0 0

- 2 5 0

0

2 5 0

5 0 0

G L - 2 4 .9 m

- 5 0 0

- 2 5 0

0

2 5 0

5 0 0

G L - 0 m

O b s e rv e d C a lc u la te d

Measured & Back-calculated Accelerogramscompared in SGK for Aftershocks and Main Shock

-100

-80

-60

-40

-20

0

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

T K S M ain Shock (01170546)

EW N S

M ax.Shear Strain(%)

Depth from G

L(m

)

-100

-80

-60

-40

-20

0

0.000.010.020.030.040.050.060.070.080.090.10

KNK Main Shock (01170546)

EW NS

Max.Shear Strain (%)

Depth from G

L (m)

-80

-60

-40

-20

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

PI M ain Shock (01170546)

EW N S

M ax.Shear Strain (%)

Depth from G

L (m)

-100

-80

-60

-40

-20

0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

SG K M ain Shock (01170546)

EW N S

M ax.Shear Strain (%)

Depth from G

L (m)

Computed Max. shear strain versus Depth in 4 vertical array sites

max0.65

effγ γ= ⋅

PI SGK

TKS KNK

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

G /G0

SG K PI KNK

C lay: Ip=40-83by Kokusho et al.(1982)

(a) C lay

Shear m

odulus ratio G/G

0

Effective shear strain γeff

D SG K PI KNK

Dam

ping ratio D (%)

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

Shear m

odulus ratio G/G

0


G /G0

SG K PI TKS KNK

Liquefied

(c) Sand

Dam

ping ratio D (%)

D SG K PI TKS KNK

1E-6 1E-5 1E-4 1E-3 0.01 0.1

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25


Sand: σc'=98 kPa

by Kokusho (1980)

Shear m

odulus ratio G/G

0


Dam

ping ratio D (%)

(b) Silt

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

Shear m

odulus ratio G/G

0


(d) G ravel

Dam

ping ratio D (%)

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

Shear m

odulus ratio G/G

0

N orm alized effective shear strain γeff/(σ'

c/p

0)0.5

G ravel: σc'=98 kPa

by Kokusho and Tanaka (1994)

(f) G ravel (Norm alized by confining stress)

Dam

ping ratio D (%)

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

SandIw asaki et al.(1978)

Shear m

odulus ratio G/G

0


c/p

0)0.5

Sandby Seed-Idriss(1970)

Sand: σc'=98 kPa

by Kokusho(1980)

(e) Sand (Norm alized by confining stress)

Dam

ping ratio D (%) G/G0~γeff

relationships for different soils

In Japan, How to evaluate strain-dependent shear modulus and damping ratio in laboratory.

1) Use triaxial device with inner load cell.

2) Employ high-sensitivity gap sensors or LDT for vertical disp. measurement.

3) Undrained cyclic loading test for f=1~0.1 Hz shear modulusand damping for wide strain range of 10-6-10-2.

4) For small strain modulus, pulse tests or bender element test are also employed. Resonant column test is not so popular.

LDT

Measured by gap sensor kokusho (1980)

Measured by conventional sensor

Shear modulus versus strain of sand for different confining stress

0

0.2

0.4

0.6

0.8

1

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02

SHEAR STRAIN; γ

SHEA

R MO

DULU

S RA

TIO; G

/G0

σc'=300 KN /m 2

σc'=200 KN /m 2

σc'=100 KN /m 2

σc'=50 KN /m 2

σc'=20 KN /m 2

0

50

100

150

200

250

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02

SHEAR STRAIN; γ

SHEA

R MODU

LUS ; G

(x 100

0 kP

a)

N o.58(e=0.645, σc'=300 KN /m 2) N o.48(e=0.651, σc'=200 KN /m 2)

N o.49(e=0.643, σc'=200 KN /m 2) N o.53(e=0.64１, σc'=200 KN /m 2)





N o.59(e=0.636, σc'=20 KN /m 2)

Toyoura sand

Hysteretic damping ratio of sand for different confining stress

0

0.05

0.1

0.15

0.2

0.25

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02

SHEAR STRAIN; γ

HYSTERETIC DAMPING RAITO; D

N o.58(σc'=300 KN/m 2)

No.48,49,53(σc'=200 KN/m 2)

No.47,50,57(σc'=100 KN/m 2)

No.51,52,55(σc'=50 KN/m 2)

No.54,56,59(σc'=20 KN/m 2)

Toyoura sand

Shear modulus ratio versus strain of clay for different Ip

0

0.2

0.4

0.6

0.8

1

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01

SHEAR STRAIN; γ

SHEAR M

ODULUS RATIO; G/G

0

S -1-1　(IP=90,σc'=16 KN/m 2) S-1-3　(IP=38,σc'=16 KN/m 2) S-2-1　(IP=96,σc'=16 KN/m 2)

S-2-3　(IP=85,σc'=16 KN/m 2) S-4-1　(IP=52,σc'=31 KN/m 2) S-4-3　(IP=54,σc'=29 KN/m 2)S-5-1　(IP=57,σc'=29 KN/m 2) S-5-3　(IP=52,σc'=36 KN/m 2) S-6-1　(IP=46,σc'=46 KN/m 2)

S-6-2　(IP=56,σc'=45 KN/m 2) S-6-1　(IP=49,σc'=46 KN/m 2) S-8-1　(IP=41,σc'=62 KN/m 2)S-9-1　(IP=NP,σc'=69 KN/m 2) S-9-2　(IP=14,σc'=68 KN/m 2) Toyoura sand σc'=100 KN/m 2

Ip > 80

Ip = 50-60

Ip = 40-50

Ip = 30-40

Ip = 10-20

N PToyoura sand

Intact Teganuma clay

Effect of confining stress on modulus degradation

0

0.2

0.4

0.6

0.8

1

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01

SHEAR STRAIN; γ

SHEAR M

ODULUS RATIO; G

/G

0

S -6-2　(IP=56,σc'=45 KN/m 2)

S-6-4　(IP=44,σc'=100 KN/m 2)

S-6-5　(IP=38,σc'=300 KN/m 2)

S-6-3　(IP=54,σc'=500 KN/m 2)

Intact Teganuma clay

Modulus & Damping ratio versus strain of gravel for different confining stress

0

0.2

0.4

0.6

0.8

1

1.2

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02

SHEAR STRAIN; γ

SHEA

R MODULU

S RATIO; G

/G0

σc'=75 KN/m 2, G 0=103 M Pa

σc'=100 KN/m 2, G 0=100 M Pa

σc'=200 KN/m 2, G 0=206 M Pa

σc'=400 KN/m 2, G 0=288 M Pa

0

0.05

0.1

0.15

0.2

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02

SHEAR STRAIN; γ

HYST

ERET

IC DAM

PING

RAITO

; h

Intact Pleistocene

gravel

1E-6 1E-5 1E-4 1E-3 0.01 0.1

0.0

0.2

0.4

0.6

0.8

1.0

Lab test results

G ravel(98kPa)

Sand(98kPa)

C lay(Ip=40-83)

(a) Shear m odulus ratio

Liquefied

C lay Silt Sand G ravel

Shear m

odulus ratio G/G

0

Effective shear strain γeff or γ

eff/(σ'

c/p

0)0.5

Back-calculated strain-dependent modulus degradations of 4 types of soils compared with previous lab tests

1E-6 1E-5 1E-4 1E-3 0.01 0.1

0

5

10

15

20

25

G ravel(98kPa)

C lay(Ip=40-83)

Sand (98kPa)

C lay Silt Sand G ravel

(b) D am ping ratio

Dam

ping ratio D (%)

Effective shear strain γeff or γ

eff/(σ'

c/p

0)0.5

Back-calculated damping ratios versus strain of 4 types of soils compared with previous lab tests

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

G /G0

SG K PI KNK


(a) C lay

Shear m

odulus ratio G/G

0


D SG K PI KNK

Dam

ping ratio D (%)

Back-calculated modulus degradation and damping compared with lab test (Clay)

1E-6 1E-5 1E-4 1E-3 0.01 0.1

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25


Sand: σc'=98 kPa

by Kokusho (1980)

Shear m

odulus ratio G/G

0


Dam

ping ratio D (%)

(b) Silt

Back-calculated modulus degradation and damping compared with lab test (Silt)

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

SandIw asaki et al.(1978)

Shear m

odulus ratio G/G

0


c/p

0)0.5

Sandby Seed-Idriss(1970)

Sand: σc'=98 kPa

by Kokusho(1980)

(e) Sand (Norm alized by confining stress)

Dam

ping ratio D (%)

Back-calculated modulus degradation and damping compared with lab test (Sand)

1E-6 1E-5 1E-4 1E-3 0.01

0.0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

20

25

Shear m

odulus ratio G/G

0


c/p

0)0.5

G ravel: σc'=98 kPa

by Kokusho and Tanaka (1994)

(f) G ravel (Norm alized by confining stress)

Dam

ping ratio D (%)

Back-calculated modulus degradation and damping compared with lab test (Gravel)

SUMMARY ON BACK-CALCULATED PROPERTIES (I)In spectrum ratios, back-calculation overestimates lower frequency peaks and under-estimates higher frequency peaks compared to observation presumably due to strain-dependency and frequency-dependency of properties.

Clear differences in S-wave velocities are recognized not only between the main shock and aftershocks but also among aftershocks of different intensities.

Damping ratios for the main shock are evidently larger than aftershocks.

Clear modulus degradations can be identified from the back-calculated S-wave velocities.

Degradations are almost consistent at 4 sites, from which soil-specific curves can be differentiated for clay, silt, sand and gravel.

SUMMARY ON BACK-CALCULATED PROPERTIES (II)Confining stresses have significant effect on the degradations of non-cohesive soils in situ, too.

Back-calculated damping ratios increase with increasing effective strains for 10-4 or larger. Damping ratio in liquefied sand layers may be back-calculated as very large values (46-52%).

The majority of back-calculated damping ratios in small strain ranges are a few percent higher than laboratory test results despite apparent splits in the back-calculated damping values (1-6%).

A fair agreement in modulus degradation can be recognized between back-calculation and lab test results for clays and sands except for large strain level.

For gravels, back-calculated degradations are milder than laboratory tests presumably reflecting appreciable fine content in in situ soils.

Higashinadadeep hole site

VsVp

Higashinada deep hole site (GL-1670m), seismometer installation levels and Vs, Vp distribution along depth

Seismometer

Acceleration amplification in deep soil ground for 3 larger earthquakes

(M>6.0, Max.Surf. Acc~10 cm/s2)

EQ1 EQ2 EQ3

Spectrum ratio (3 larger earthquakes M>6.0)

Spec

trum

ratio

Spec

trum

ratio

Spec

trum

ratio

Spec

trum

ratio

GL-0m/GL-20m

GL-0m/GL-50m GL-0m/GL-1670m

GL-0m/GL-750m

Variation of D0 and m along depth for frequency-dependent damping ratio

0.01 0.1 1

0

500

1000

1500

2000

Damping at f=1.0 Hz (D0) or m

Depth(m)

0mD D f −=

mD0

Dam

ping

ratio

x 2

In situ frequency-dependent damping ratio based on previous papers (Fukushima and Midorikawa, 1994)

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

0.0 0.5 1.0 1.5 2.0 2.5

Density

Density(t/m3)

Depth(m

)

0 1000 2000 3000

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0 S-wave velocity

Vs(m/s)

Soil model, Vs and density distribution along depth

0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0

- 6 0 0

- 4 0 0

- 2 0 0

0

2 0 0

4 0 0

6 0 0 (a ) m a x = 6 0 9 .4 (c m / s 2 ):tim e = 5 .3 2 (s)

Acc

eleration (cm

/s2)

T im e (s)

0.1 1 100

50

100

150

200

250

300 (b)

A nalyzed frequency range(U p to 20 H z)

Fourier spec. (cm/s2*s)

F re quency (H z)

Accelerogram and Fourier spectrum of input motion (PI)

1

10

100

1000

0.1 1 10 100

Dep

th fr

om G

L (m

)

Damping ratio D0 (%)

Kokusho & Matsumoto 1998

Kokusho et al.1992Yamamizu et al.1983

Shear strain:

γ≤10 −4

γ>10 −310−3≥ γ≥10 −4

(1995 Kobe EQ)

Damping ratio in deep soil ground assuming 0mD D f −= ⋅

-1400

-1200

-1000

-800

-600

-400

-200

0

0.0 0.2 0.4 0.6 0.8 1.0

Case-A

m =0.5 m =1.0

(G0-G)/G

0

Depth(m

)

( )0.5r vγ σ ′∝For cohesive soils,too.-1400

-1200

-1000

-800

-600

-400

-200

0

0.0 0.2 0.4 0.6 0.8 1.0

Case-B

m=0 m=0.5 m=1.0

(G0-G)/G

0

Depth(m

)Degree of

nonlinearity

versus depth

( )0 0G G G−

.r co n stγ = for cohesive soils.

( )0.5r vγ σ ′∝ for cohesive soils,too.

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

100 1000 10000

Linear

Equivalent linear

Case-A

m=0 m=0.5 m=1.0

M axim um acceleration (gal)

Depth(m

)

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

100 1000 10000

Linear

Equivalent linear

Case-B

m=0.0 m=0.5 m=1.0

M aximum acceleration (gal)

Depth (m)

Effect of m on Max. Acc. versus Depth relationship

.r co n stγ = for cohesive soils.

( )0.5r vγ σ ′∝ for cohesive soils,too.

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

0 1000 2000 3000 4000 5000 6000

Linear

Equivalent linear

M axim um Acceleration (gal)

Depth(m

) Basic case * 1/2 * 1/4

Effect of reducing damping ratio on

Max.Acc. distribution

10 100 10000.1

0.2

0.4

0.6

0.81

2

Dam

ping ratio D

0 (%)

Basic value (from Fig.4) ｘ1/2 ｘ1/4

D epth(m )

0.0 0.2 0.4 0.6 0.8 1.00

500

1000

1500

2000

2500

3000

3500(cm /s2)

Maximum

base acceleration

C onstant m

γ'=const.: for cohesive soils. : for cohesive soils, too.( )0.5r vγ σ ′∝

0mD D f −= ⋅

Effect of m on Max. Base Acc. (GL-1670 m)

SUMMARY ON RESPONSE IN DEEP SOIL GROUND

Even during the destructive Kobe earthquakes, calculated modulus degradation is milder than 20% deeper than about 300m.

Acceleration tends to increase with increasing depth in analyses based on frequency-independent damping, indicating that the damping should inevitably be frequency-dependent in analyzing deep ground.

Assumptions on soil properties such as frequency-dependency in damping or reference strain have a great effect in analytical seismic response in deep soil ground.

SUMMARY & FURTHER RESEARCH (I)

In Situ PropertiesLaboratory modulus degradation for individual soil types are applicable to the field at least up to medium strain range. Field damping is only qualitatively consistent with lab test damping.

More quantitative research for in situ properties; -Modulus degradation for large strain range considering

strain-dependency and PP-buildup. --Damping ratio for small strain and its mechanism -Large strain damping considering cyclic mobility and

PP-buildup.

SUMMARY & FURTHER RESEARCH (II)In vertical motions, little nonlinearity of amplification and back-calculated Vp.

Deep Soil PropertiesStrain-dependent soil nonlinearity may be ignorable in depth of a few hundred meters of soil ground even during destructive earthquakes.

Based on deep-hole data analyses, damping is no doubt frequency-dependent.

Effect of high overburden stress on modulus and damping in deep soil should be investigated further.

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