Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

Study on Seismic Countermeasures by Steel Pile Diaphragm Wall in Coastal Levee
Kyu-Tae LEE
Techinical Director, Osaka main office, CTI Engineering Co., Ltd, Osaka, Japan

Yoshiyuki OKAJIMA
Group Leader, Waterworks Engineering Division, CTI Engineering Co., Ltd, Osaka, Japan
Email: okajima@ctie.co.jp

Shunichi AKIBAEngineer, Waterworks Engineering Division, CTI Engineering Co., Ltd, Osaka, Japan

Takeshi KODAKA
Professor, Department of Civil Engineering, Meijo University, Aichi, Japan

ABSTRACT
After the 2011 off the Pacific coast of Tohoku Earthquake, for existing coastal levees, performance-based seismic
designs have been carried out to counter this level II earthquake with a Tsunami, and earthquake resistance measures
are being implemented in preparation for The Nankai Trough earthquake which is expected to occur at 70% probability
in the next 30 years. In this research, as earthquake countermeasures for the coastal levee against liquefaction of thefoundation ground during the earthquake by the press-in type steel pile, setting of the required performance at the timeof earthquake, examination of performance-based seismic design and countermeasure construction study were carriedout. First, we estimated the extent of damage by the numerical analysis method that the levees suffered with inertia
force and ground liquefaction accompanying the earthquake, then we found out the necessity for earthquake resistancemeasures with the levees according to the performance requirements. In this paper, we mainly describe difference incalculated behavior of the levee due to analytical modeling methods about components of the coastal levee such as
sands embankment, wave-dissipating block and concrete revetment. In addition, we show effects of press-in type steel
pile as earthquake countermeasures by the numerical analysis method.
Key words: Coastal levee, seismic countermeasure, numerical method, liquefaction, press-in type steel pile

1. Outline of the projectneighboring main roads, press-in type steel pile is shown

1.1. Background and objectives of the projectas an example of the earthquake countermeasure method,

In recent years, in preparation for a huge earthquake

the concept of the performance regulation against theby the Nankai Trough after the Tohoku Region Pacificseismic embankment earthquake, the concept of the

Offshore Earthquake, seismic performance checks against

seismic performance check, and the method of modelinglevel 2 earthquake motions and seismic countermeasuresthe existing structure and countermeasure work in theaccompanying the check result are implemented in theanalysis will be described.

existing coastal protection. In this research, in setting
seismic performance countermeasures according to theseismic performance evaluation of the coastal levees and1.2. Structure
On the coastal levee, the nourished beach in the front

the seismic countermeasure accompanying the inspectionof the revetment is equipped with wave dissipating

result, considering the structure characteristics of theconcrete blocks. In addition, the back side has main roads

coastal levees, the surrounding environment includingwhich are important in the living environment of the- 273 -

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

surrounding residents, and the other side is the residential

extremely low. This corresponds to the tsunami in thearea. Fig. 1 shows the target section plan. The structure ofGreat East Japan Earthquake. On the other hand, thethe coastal levee is a special breakwater of the parapet

occurrence frequency is higher than that of "the largest

type as shown in Fig. 2.

class tsunami", and the earthquake tsunami causing greatdamage, although the tsunami height is low, is called theplanned tsunami. This tsunami occurs at frequencies of
decades to hundreds of years.
In this study, we aim to prevent tsunami damage tocoastal levees, targeting the planned tsunami by the
Nankai Trough. From the viewpoint of protecting coastal
levees from damage of the tsunami, the following two
points were set as the performance required of the coastal
levees after the earthquake. ① Tsunami does not overflow,②

Coastal levees maintain soundness after theearthquake.
Fig. 1

Section plane2.2. Setting performance regulations for coast levees
In order to satisfy the required performance set in theprevious section, the following performance wasspecified.
① How to confirm that the tsunami does not overflow
Confirm that the coastal levees height after the
Fig. 2earthquake is higher than the design tsunami water level.

Cross section

The amount of settlement due to the earthquake is the sumof settlmetnt due to liquefaction and broad ground

2. Concept of countermeasures against earthquake

settlement. Evaluation of settlement by liquefaction shalltsunami in coastal levees
2.1. Required performance
In the Nankai Trough, the Philippine Sea plate getsbe the average of three settlement amounts (δy1, δy2,δy3).

under the plate on the continental side, and the edge of theHere, the allowable liquefaction subsidence amountplate on the continental side is drawn. For this reason, theis 0.5 m because the current levee height is T. P. +10.5 m,

strain gradually accumulates, reaching the limit and trying

the design tsunami water is level T.P + 8.0 m, and theto return to the original, then a trench-type hugebroad ground settlement is -2.0 m.

earthquake accompanied by a tsunami occurs. The Nankai② Confirmation that the coast levee is soundTrough Earthquake occurred at intervals of about once
every 100 years, more than 70 years have passed since theConfirmation by horizontal displacement (ensuringcontinuous soundness of cut-off wall)

last occurrence, and it is expected to occur with a

Maximum value of δX1 or δX2 ≤ 0.50 m

probability of about 70% over the next 30 years. The
Cabinet Office Central Disaster Prevention Council

δ y1
δ x1

δ y2

δ y3

presented the idea of a new tsunami countermeasure on
September 28, 2011, following the massive tsunami

Deformation after the earthquake

caused by the Great East Japan Earthquake that occurredon March 11, 2011. There are basically two levels
assumed for building future tsunami countermeasures.
First of all, the "largest class tsunami" that causes
maximam damage, although its occurrence frequency is- 274 -

δ x2

Fig. 3

Concept of performance regulation

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

waveform is shown in Fig 5.

3. Performance check of coast levees
As a performance check of the coastal levees, weshow the results of liquefaction determination offoundation ground, simple evaluation of levee settlement

Table 1.

Analytical parameters of the ground part1

amount and detailed evaluation of levee settlement

wet
densityρ3（t/m )

porositynvelocity of Young's
S-wave modulus
E
Vs
2
(m/s)
(kN/m )

standardinitial
Poisson’s
shear
ratio
modulusv
Gma(kN/m2)- 1.63E+05
0.333

amount.

soil
layer

3.1. Analysis conditions

B

12

1.9

0.45

230

Ags

12

0.21

1.9

0.45

230

-

1.63E+05

0.333

Ag1-m

21

0.25

2.0

0.45

230

-

1.04E+05

0.333

As1

28

0.28

1.9

0.45

260

-

9.39E+04

0.333

Ac

9

1.7

0.55

290

-

8.88E+04

block

-

1.9

-

-

3.36E+04-

parapet

-

2.3

-

-

2.35E+07

-

0.167

Dg

-

2.2

-

-

-

-

The ground model to be studied is shown in Fig. 4.
At this position, an alluvium layer (Ags layer, Ag1-m
layer, As layer) that becomes a liquid layer is deposited
just under the embankment.

NvalueTable 2.

640

0.333
-

Analytical parameters of the ground part2

angle ofcohesion hysteresis
shearc
resistance
damping2
φfhmax(kN/m )
(°)

soil
layer

Fig. 4RL 20

parameters of liquefaction
φp
(°)

W1

p1

p2

c1

S1

B

41

0

0.300

-

-

-

-

-

-

Ags

41

0

0.300

28.0

2.500

1.200

0.700

1.900

0.005

Ag1-m

41

0

0.300

28.0

3.500

0.700

0.700

2.000

0.005

As1

40

0

0.300

28.0

8.500

1.200

0.900

1.900

0.005

Ac

30

0

0.200

-

-

-

-

-

-

block

-

-

-

-

-

-

-

-

-

parapet

-

-

-

-

-

-

-

-

-

Dg

-

-

-

-

-

-

-

-

-

Ground model

The parameters set from the soil test are shown in

600

Max:461gal

400

ACC.(gal)

Table 1, Table 2. Also, as an indication of liquefaction,
an average N value, RL20 is shown. RL20 is the

200
0

-200

liquefaction intensity ratio by cyclic triaxial test, it is the-400

repetitive stress amplitude ratio when repetition or

-600

0

50

100

150

200

250

300

Time(sec)

number of times is 20 and the amplitude of axial strain is 5
to 6%. As the value of RL20 is smaller, liquefaction tends

Fig. 5

Input ground motion on the base surface

to occur. N value converted to effective soil pressure 100
kN/m2 is called converted N value, N1. The relationshipthat RL20 is about 0.2 when N1 is 10, and RL20 is about 0.4

100.0

bridge Part Ⅴ seismic design. So, it can be said that theAgs layer and the Ag1 - m layer are small in RL20 andeasily liable to be liquefied.
The earthquake ground motion to be considered wasa seismic waveform assumed from the Central Disaster

Passing percentage(％)

when N1 is 20 are shown in Specification for Highway
High Possibilty

75.0

50.0

of liquefaction
Possibilty ofliquefaction

Ag1(7m)Ag1(12m)

25.0

Prevention Council in the Tonankai / Nankai earthquake
published in 2003. The maximum acceleration was 461

As1(17m)
As1(20m)
0.0

0.001

0.01

0.1

1

10

100

Grain size(mm)gal, the duration was 120 seconds, the top surface of thebase was the input position. The input ground motion- 275 -

Fig. 6

Liquefaction determination by grain sizeProceedings of the First International Conference on Press-in Engineering 2018, Kochi(2)

𝑅 = 𝑐𝑤 𝑅𝐿

3.2. Liquefaction determination(1) Determination by Grain size distribution of soil
If the range of the particle size curve is within therange of "possibility of liquefaction", it is judged tosmall and medium scale earthquakes and trench
type large earthquakes
𝑐𝑤 = 1.0

liquefy. Fig. 6 shows the particle size accumulation curvesof Ag1 layer and As1 layer. From this, it is judged that
there is a possibility of liquefaction occurring in these(2.1)

large scale earthquake with active fault
1.0 (𝑅𝐿 ≤ 0.1)

layers.

𝑐𝑤 = 3.3𝑅𝐿 + 0.67 (0.1 < 𝑅𝐿 ≤ 0.4)
1.0 (0.4 < 𝑅𝐿 )(2) Determination by N-value
As judged by grain size, it was judged that"possibility of liquefaction", so liquefaction was judged

𝑅𝐿 = 0.082√0.85𝑁𝑎 + 2.1)/1.7(𝑁𝑎 < 14)by using N value by boring and earthquake acceleration.
Table 3 shows the liquefaction determination result.
𝑅𝐿 = 0.082√
Liquefaction determination by N-value

Table 3.

𝑁𝑎+ 1.6 × 10−6 ∙ (𝑁𝑎 − 14)4.5
1.7(14 ≤ 𝑁𝑎 )：water level

Layer

depth
(m)

wet
unit
weightＮ-Value３γ(kN/m )Ags

Ag1m-uAg1m-l

As1

1.3
2.3
3.3
4.3
5.3
6.3
7.3
8.3
9.3
10.3
11.3
12.3
13.3
14.3
15.3
16.3
17.3
18.3
19.3
20.3
21.3
22.3
23.3
24.3
25.3
26.3
27.3
28.3
29.3
30.3
31.3
32.3
33.3
34.3
35.3
36.3
37.3
38.3
39.3
40.3

19.0
19.0
19.0
19.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
18.5
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0

3
5
7
6
16
18
25
29
15
13
19
9
16
16
10
22
21
21
12
26
35
29
30
29
25
21
23
23
29
19
23
22
23
22
33
14
24
19
24
18

fine
fractioncontent

averagegraindaiameterFC(％)

D50(mm)(2.2)

Dynamic
shear
strength
ratio
R

Seismicshear
stressratio
L𝐶𝑤 : Correction coefficient by earthquake groundResistivity
againstliquefaction
FLmotion characteristics
𝑅𝐿 : liquefaction intensity ratio by cyclic triaxial test
𝑁𝑎 : Corrected N value in consideration of influence

3.4
9.2
9.2
3.7
3.7
3.7
2.9
5.5
5.5
2.1
2.1
3.7
3.7
3.7
4.2
5.9
5.9
7.2
7.2
28.4
28.4
33.8
33.8
33.8
32.1
32.1
32.1
15.0
15.0
15.0
15.0
27.3
27.3
38.7
38.7

1.80
1.80
1.80
0.81
0.81
0.81
1.50
0.78
0.78
3.20
3.20
12.00
12.00
12.00
4.20
2.30
2.30
3.30
3.30
0.13
0.13
0.11
0.11
0.11
0.11
0.11
0.11
0.15
0.15
0.15
0.15
0.14
0.14
0.10
0.10

0.272
0.325
0.370
0.231
0.210
0.249
0.168
0.219
0.215
0.160
0.233

0.231
0.278
0.249
0.242
0.234
0.270
0.247
0.266
0.263
0.291
0.233
0.252
0.245
0.209
0.202
0.244
0.160
0.233
0.208
0.252
0.221

0.239
0.275
0.299
0.313
0.323
0.329
0.333
0.334
0.335
0.333
0.330

0.315
0.310
0.305
0.300
0.295
0.290
0.285
0.280
0.275
0.270
0.264
0.259
0.253
0.247
0.241
0.235
0.229
0.223
0.217
0.211
0.204

1.14
1.18
1.24
0.74
0.65
0.76
0.50
0.66
0.64
0.48
0.71
0.73
0.90
0.81
0.81
0.79
0.93
0.86
0.95
0.96
1.08
0.88
0.97
0.97
0.85
0.84
1.04
0.70
1.05
0.96
1.20
1.08

of granularity
0.83

(3)

𝐿 = 𝑟𝑑 𝑘ℎ𝑔𝐿 𝜎𝑣 /𝜎𝑣′
𝑟𝑑 = 1.0 − 0.0015𝑥

0.59

(3.1)

𝑟𝑑 : Reduction coefficient in the depth direction of

0.81

the shear stress ratio at the time of earthquake
𝑘ℎ𝑔𝐿 : Standard value of design horizontal seismic
intensity used for judgment of liquefaction(ground surface: Approximately 0.4～0.8)
𝜎𝑣 /𝜎𝑣′ : The value obtained by dividing the total

0.96

overpressureof the depth of x from the groundsurface by the effective loading pressure

If the FL value is less than 1, liquefaction occurs, andFrom this, it is judged that the Ags layer, the Ag1m

if it is small, the degree of liquefaction is intense. FL value

layer, the As layer are liquefied and the Ag- u layer whichis the resistivity to liquefaction and is obtained by Eq. (1).

is the upper layer in the Ag layer is considerably liquefied.

𝐹𝐿 = 𝑅/𝐿(1)

3.3. Simple evaluation of levee subsidence amountIn order to predict the amount of deformation of the

𝐹𝐿 : the resistivity to liquefaction

coastal Levees at the time of the earthquake with high

R: dynamic shear strength ratio obtained by Eq. (2)accuracy, it is necessary to carry out highly accurate

L: the shear strong stress ratio at the time ofseismic diagnosis for each individual facility at a greatearthquake obtained by equation (3)cost and time. Therefore, there is a method of executing
simulation under various conditions in advance, and- 276 -

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

performing seismic diagnosis by making the calculation

wave dissipating concrete block

result of the deformation amount into a database. Here, bycomparing the condition of the facility with the database,the deformation amount of the coastal levees at the time of

0.8m

the earthquake is calculated. This method is called a charttype seismic diagnosis.
As a condition for the simple evaluation, the groundheight, liquefaction layer thickness, N value, revetment
gradient, earthquake motion (speed PSI value of the time
history waveform shown in Fig. 5) were set using thesimplified evaluation model shown in Fig. 7. As a result

Fig. 8of the calculation, subsidence due to liquefaction of 0.8 m

Deformation of the block as liner element

occurred at the top of the parapet. This resulted inexceeding the permissible liquefaction sinking amount of

On the modeling of concrete and soil of coastal

0.5 m, so it is carried out by the time history response

levees, the authors have been studying dynamic

analysis.

interaction between soil elements and concrete elements.
A joint element is provided at the boundary between
concrete and soil to make a model that appropriately
expresses dynamic interaction. Fig. 9 shows the analysis
model of current levee.

Fig. 7

Model in Simple Evaluation

3.4. Detailed evaluation of levee subsidence amount
Apply the time history seismic response analysis
Fig. 9method as detailed evaluation. Because the foundation

Analysis model of the current leveeground structure is liquefied, we evaluate the deformation

The analysis results of the current coast levees areof the coastal levees using the effective stress method

shown in Fig. 10. Focusing on the deformation around the(analysis code: FLIP).

revetment, the liquefaction layer becomes fluidized andAs a preliminary analysis, Fig. 8 shows the result of

the embankment on the back of the revetment settles. On

modeling the wave dissipating concrete block with linear

the other hand, the nourished beach in the front of theelements. Focusing on the deformation mode, the coastal

revetment works in a direction to suppress the flow oflevees are deformed by being pulled by the horizontal

seawall to the sea side. As a result, the parapet revetment

displacement of the block. Actually, the block and themoves with rotation, the horizontal displacement is 0.71 m

ground are discontinuous, and such deformation is(tolerance is 0.5 m) and the vertical displacement is 0.7 m

unthinkable. For seismic performance, we focus on the(tolerance is 0.5 m). The current levee does not satisfy thehorizontal / vertical displacement of the coastal levees, so

performance after the earthquake.

we do not consider the deformation of the block andconsider it as the node mass.

- 277 -

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

are placed in front of the levees. The steel pile has adiameter of 800 mm and a length of 16 m. The steel pilepenetrates into the As layer which is hardly liquefied ascompared with the Ag layer.
The analysis result is shown in Fig. 14. The
horizontal displacement is 0.75 m, and the verticaldisplacement is 0.42 m. Vertical displacement decreases
and it is less than 0.5 m which is the allowable value, buthorizontal displacement is larger than 0.5 m, and seismic
performance is not satisfied.
Fig. 10Analysis results of the current coast levees

4. Study of countermeasures
4.1. Primary selection of countermeasures
As countermeasures for suppressing

grounddeformation caused by liquefaction, it is conceivable to(1) inhibit liquefaction by ground improvement, (2)inhibit deformation by steel piles, (3) raise theembankment, (4) adding wave dissipating concreter
blocks as suppressing deformation of coastal levees.
Suppression of liquefaction caused by ground
improvement is not improved from the viewpoint ofFig. 11

Analysis model of adding blocks

Fig. 12Analysis results of adding blocks

economic efficiency and construction feasibility because
it will be improved immediately under the embankment
where the influence on the prefectural road traffic function
is great. When adopting leve raising, the necessary raisingheight is 20 cm, but it is difficult to secure the soundness(horizontal displacement) of the coast levee. For thisreason, we selected (2) suppression of deformation bysteel pilels and (4) adding wave dissipating concreter
blocks as countermeasures.
4.2. Study of countermeasures by adding blocks
Fig. 11 shows an analytical model to which blocks
are added. These blocks are also taken into account by thenode mass.
The analysis result is shown in Fig.12. The
horizontal displacement is 0.92 m, and the verticaldisplacement is 0.84 m. The deformation is the same as
the current section, and the deformation suppression effectby the wave-blocking block is not obtained.
4.3. Study of countermeasures by steel piles(1)Place steel pile in front of the levees

Fig. 13

Fig. 13 shows an analytical model where steel piles- 278 -

Analysis model of steel pile in front of the levees

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

displacement

andhorizontal

displacement

were

suppressed, but since cavities occurred under therevetment, it is considered that the revetment will actually
be destroyed.
From the above, it is difficult to expect the functionof the existing parapet after the earthquake. Therefore, we
decided to set up a new parapet on the steel pipe as shownin the Fig. 17.
Fig. 14Analysis results of steel pile in front of the levees

The analysis result is shown in Fig. 18. The
horizontal displacement is 0.49 m, and the verticaldisplacement is 0.17 m. Both of them satisfied theallowable displacement, which resulted in being able toprevent the damage caused by the tsunami.

Fig. 15

Analysis results of steel pile at levee crowndisconnect with parapet

Fig. 16

Fig. 17

Analysis model of steel pile with parapet

Fig. 18

Analysis results of steel pile with parapet

Analysis results of steel pile at levee crownconnect with parapet

5. Concluding remarks
We examined tsunami countermeasures against the(2)Place steel pile at the levee crowncoastal levees which are restricted by selection of

As a preliminary analysis, a steel pile was placedcountermeasures because there are arterial roads andbehind a concrete parapet. The steel pile is not connectedhouses. As a result, the method of placing the steel pile atwith the parapet. As shown in Fig. 15 , it was found thatthe top of the levees with parapet was the only way to

the ground on the front side of the steel pipe greatly

satisfy the performance regulations. The construction of

moved in the horizontal direction.

this steel pile was planned to be carried out by the

Next, the analysis results of a steel pile at levee
crown connect with parapet are shown in Fig. 16. Verticalgyropress method in order to secure the service of theroad.

- 279 -

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

References
Japan Road

Association.

2002.

Specificationfor

Highway bridge Part Ⅴ seismic design. 406p.
Maruzen. (in Japanese)
Japan

Road

Association.

2017.

Specificationfor

Highway bridge Part Ⅴ seismic design. 302p.
Maruzen. (in Japanese)
The Overseas Coastal Area Development Institute ofJapan.

2009.

Technical

Standards

andCommentaries for Port and Harbour Facilities inJapan. 980p. Japan Association of Ports andHarbors.
M., Higashijim, I., Fujita, K., Ichii, S., Iai, T., Sugano
and M., Kitamura. 2006. Development of a simple
seismic performance evaluation technique forcoastal structures. Proceedings of civil engineeringin the ocean vol. 22, pp. 511-516.
S., Akiba, K., Lee, Y., Okajima, T., Koyama. and Y.,
Onishi. 2013. A study on the earthquake-resistantmethod of sea wall. Proceedings of the Japan
National Conference on Geotechnical Engineering,pp. 1229-1330.
M., Ueno, K., Lee, Y., Okajima, M., Nakagami H.,
Tagawa, M., Muneyuki and T., Kodaka. 2016. Studyon the Counterweight Fill Method forLiquefaction
Countermeasure of Sea Wall Proceedings of theJapan

National

Conferenceon

GeotechnicalEngineering, pp. 1083-1084.

- 280 -