THE EFFECTS OF SOIL DENSITY ON LIQUEFACTION INDISE LEVEE

1 2 3 3 Hiroyuki ARAKI, Shunsuke TANIMOTO, Masanori ISHIHARA and Tetsuya SASAKI

1

305-8516 1-62

3

The river levees located on non-liquefiable foundation layer were damaged by the 2011 off the Pacific coast of Tohoku Earthquake because liquefaction occurred at the saturated zone inside the river levee. The mechanism of the liquefaction inside a levee has not been clarified fully. In this study, a series of centrifugal model tests was conducted in order to evaluate the effects of soil density on the liquefaction inside a levee. The density of a bottom part of the levee with the degree of compaction (Dc) of 90 % decreases by 3 to 4 % due to the consolidation of the clay foundation layer below the levee. After shaking, crest settlement of the levee with Dc of 90 % was approximately half of that of the levee with Dc of 85 %. In the case of the levee with Dc of 90 %, deformation of liquefaction zone at the bottom of the levee was restrained by the un-liquefaction zone located at the toes of the slope.

Key Words : Levee, Earthquake, Liquefaction, Soil density, Centrifugal model test

(1) (2)

(3)

1)

2011

2) 1993

3)

2011

1) 2011

4)

Okamura et al.5)

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1)

1.0 m50 G

5.0 m

5.0 m 2 8.0 m

A1

DL3:1 s=2.635 g/cm3

Fc=100 % IP=7.5A-b dmax 1.723 g/cm3

wopt 16.9 %16 % Dc

85 % 90 %Dc

s

=2.746 g/cm3 IP=15.8 Cc=0.183cu/p=0.44 6)

s=2.606 g/cm3 IP=51.5 Cc=0.394 cu/p=0.23

cu/p

1m

G.L.-1.0 m

2.5 m 1.0 m

2.5 m

1)

40 kPa90%

2)

3)

4) CO2

50 kPaG.L. 1.0 m

5) 0.1 G/min 50 G

80 85 kPa

6) G.L.

Dc = 85% Dc = 90% ccu (kPa) 1.60 2.21

cu ( ) 14.0 19.7 RL20 0.136 0.141

(cm/sec) 4.2 10-5

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Case 2-1 Case 2-2Dc 90 %

Case 2-1 6)

Case 2-26)

G.L.+3.5 m260

Case 2-4 Case 2-8 Dc 85 % 90 %

2-1 (II ) 7) TR

0.9P2 P10

Case 2-1 Case 2-2Case 2-

1 30 DV13 DV5

0.1 %

17.3 mm 20 mm

Dc=80.6 %3

3 80.2 %1 %

G.L.+0 2.5 m

Case 2-2 3.5 m

260

Case 2-1

90.6 % Case 2-1 Dc

87 % 90.0 % Case 2-286 %

Case 2-1 0.2 m Case 2-2 0.3 mCase 2-2

6.25 m0.8 %

Dc (%)

Case 2-1 90.6 Case 2-2 90.0 Case 2-4 84.7 Case 2-8 89.6

78.0

78.5

79.0

79.5

80.0

80.5

81.0

81.5

82.0

0 1 2 3 4

Dc

(%)

Test No.

Dc=80.6%(1.388g/cm3)

Dc=80.2%(1.381g/cm3)

a) Case 2-1

b) Case 2-2

Case 2-1, Case 2-2

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Case 2-1Case 2-2

G.L.+0 2.5 mCase 2-1 Dc 89 91 % Case 2-2 Dc

88 90 %

1.0 m

1.0 m0.2 0.3 m

Case 2-4 1.1 m Case2-8 1.2 m Case 2-4 3 5 m

3DV1 DV3

2.3m

Case 2-8 Case 2-4

DV1 DV3 1.1 m

A1P2 P10 DV1 3

v’v’

v’Case 2-4 12 sec u v’

15 secDV1 3

u 15 secP5 8 u 12

20 secv’ 40 sec

u v’

Case 2-8 u 10 sec15 sec

P2 3 9 10 15 secu

P4 5 7 8u 15 sec 20 sec 25 secv’ 50 sec

DV1 3 u15 sec

a) Case 2-4

b) Case 2-8

a) Case 2-4

b) Case 2-8

- 500 -

P6 10 sec u

P6

DV4DV5

Case 2-4 Case 2-8 DV4 5DV1 3

DV5 Case 2-4 0.14 mCase 2-8 0.26 m DV4 Case 2-4

0.22 m Case 2-8 0.12 m

Case 2-1 Case 2-2Case 2-2

Case 2-4 2-8

WCase 2-4 0.2 m

Case 2-8 0.6 m Case 2-8 Case 2-4

-200

20406080

100

v' ( )v' ( )

P2 P10

020406080

100v' ( ) P3

P9

020406080

100

(kPa

)

v' ( )

v' ( )

P4 P8

020406080

100v' ( )

v' ( )

v' ( )

P5 P7

020406080

100v' ( )

v' ( )

P6

-0.50

0.51

1.52

2.53

DV1 DV4 DV2 DV5 DV3

(m)

0 5 10 15 20 25 30 35 40 45 50

-500

0

500

(sec)

(gal

)

A1

DV3

-200

20406080

100

v' ( )v' ( )

P2 P10

020406080

100v' ( ) P3

P9

020406080

100

(kPa

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v' ( )

v' ( )

P4 P8

020406080

100v' ( )

v' ( )

v' ( ) P5 P7

020406080

100v' ( )

v' ( )

P6

-0.50

0.51

1.52

2.53

DV1 DV4 DV2 DV5 DV3

(m)

0 5 10 15 20 25 30 35 40 45 50

-500

0

500

(sec) (g

al)

A1

Case2-4 Case2-8

2 3 4 5 6 7 8 9 10 11-20

0

20

40

60

80

100

u,

v' (k

Pa)

u 0.0sec 10.0sec 12.0sec 15.0sec 20.0sec 30.0sec 40.0sec

v' v'( ) v'( )

2 3 4 5 6 7 8 9 10 11-20

0

20

40

60

80

100

u,

v' (k

Pa)

u 0.0sec 10.0sec 12.0sec 15.0sec 20.0sec 30.0sec 40.0sec

v' v'( ) v'( )

Case 2-4 Case 2-8

20 25 30 35 40 45 50 556789

101112131415

(m)

(m)

Case2-2(Dc=90%) Case2-4(Dc=85%) Case2-8(Dc=90%)

Case2-4 Case2-8

P2P6

P10P5 P7P4P3 P8 P9

a) b)

201114.6k b) a)

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Case 2-8 1.1 m

2011

14.6k

Dc 90% Case 2-8

P2 39 10 Case 2-1 Case 2-2 Dc

P4 5 7 8Case 2-1 Case 2-2 Dc 3 4 %

Case 2-8

Case 2-8

Dc 85 % Case 2-4

Case 2-4

1) Dc 90 %

0.2 0.3 m

Dc 3 4 %

2) Dc 85 %Dc 90 %

Dc 85 % 3) Dc 90 %

4)

Dc 90 %

1) , 18 ,

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4)

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6) 47

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