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

Study on Reinforcement of Fishery Harbor Wharf against the Nankai TroughEarthquake
Kojiro OKABAYASHI
Professor Department of civil engineering Kochi National College of Technology, Kochi, Japan
Email: oka@ce.kochi-ct.ac.jp

Koji MIKASAStudent of Advanced course Department of civil engineering Kochi National College of Technology, Kochi, Japan
Email: s1820@gm.kochi-ct.jp

ABSTRACTThe Great East Japan Earthquake has implied the big potential all over Japan for earthquakes with magnitude 9.0. In theGreat East Japan Earthquake, ports and fishing ports played an important role in (1) transportation of emergency supplies
after the earthquake, (2) early recovery of marine products lifting and distribution functions. Kochi Prefecture has
approximately 713 km coastal-line on which 88 fishing ports are scattered and 46,000 people live in this area. The fishingports are very important as the life base of local populace for the relief activity, restoration-reconstruction and business
continuity plan. The fishing ports are desired to maintain function when subject to the earthquake motion and tsunami ofthe Nankai Earthquake. In Kochi Prefecture, not only major ports but also fishing ports are proposed to be used as
earthquake resistant quay walls in the event of a disaster. This research was executed for the Kaminokae Fishing Village,
which is a typical district of the local fishing port in Kochi Prefecture. In the preparation of the earthquake resistant
wharf, low construction cost and a short construction term would be anticipated. One of the effective methods for theeconomical construction of an earthquake resistant wharf is the adoption of the press-in pile.
Keywords: Fishery harbor wharf, Nankai Trough Earthquake, effective stress analysis, Liquefaction, Centrifuge

1. Background and outline of the project
The Nankai Earthquakes, of which epicenters are in

was assumed in Kochi Prefecture. It is assumed that thethe Nankai Trough offshore in the Tosa Bay, have occurred

acceleration of 800 gals or more, a long period wave of 2-

repeatedly every 100-150 years. The Japan government

5 seconds, and continues for about 120-150 seconds(level

officially announced that the next earthquake will occur

Ⅱ). The height of the maximum tsunami is 10-34 m.

Nankai Earthquake ground motion has a maximum

with a 70% probability within the next 30 years.

The Great East Japan Earthquake has implied a big

According to “The second earthquake assessment ofearthquake potential all over Japan with a magnitude of

Kochi Prefecture”, it is assumed that the Nankai

9.0. In the Great East Japan Earthquake, ports and fishing

Earthquake ground motion has a maximum acceleration ofports played an important role in (1) transportation of

400 gals or more, long period waves with a period of 2-3

emergency supplies after the earthquake, (2) earlyseconds, and continues for about 90 seconds (levelⅠ).

recovery of marine products lifting and distribution

The height of the maximum tsunami is 6-10 m (Kochifunctions.

Prefecture, 2005).

Kochi Prefecture has approximately 713km of coast

After the Great East Japan earthquake in 2011 hadline on which 88 fishing ports are distributed and 46,000

occurred, a Nankai Trough huge earthquake (M9.0 class)people live in this area. The fishing ports are expected to- 297 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochisuffer serious damage from the earthquake motion andthetsunami

causedbytheNankai

Earthquake(Okabayashi et al. 2004).
In Kochi Prefecture, not only major ports but also

(Okabayashi et al. 2008). The samplings of soil were doneat the following depths:1). 8.5-10.5m at the second layer (sand)2). 10.8-17m at the third layer(silt)
3). 21.8-24.0m at the fifth layer (silt)

fishing ports are proposed to be used as earthquake

Table 1.

Grain size analysis

resistant quay walls in the event of a disaster. The designof port structures such as breakwaters is to target levelⅠ
earthquake ground motion, with a policy to compensate
for level 2 earthquake motion by evacuation.
This research was executed for the Kaminokae
Fishing Village, which is a typical district of the local
fishing port in Kochi Prefecture. In this area, the strong
possibility of liquefaction is observed in most of the area.
(Ministry of Transport,1997) (Okabayashi et al. 2008).
Using the existing data, we examined the effect ofliquefaction countermeasures on a construction method inwhich sheet pile and counterfort are connected by tie rods.
(Japan Road Association, 2014) (Okabayashi et al. 2014).
2. Site condition and investigations
The points of borings in Kaminokae Fishing Village
are shown in Fig. 1. The four borings (Nos. A-D) to reachthe bedrock were performed in addition to 23 existing
borings to confirm the soil strata for doing the necessary
soil test.

Fine fraction content : FC(%)
D10 (mm)
Silt mixing Sandy gravel
D50 (mm)Plasticity index : Ip
Fine fraction content : FC(%)
D10 (mm)Sand
D50 (mm)Plasticity index : Ip
Fine fraction content : FC(%)
D10 (mm)Silt
D50 (mm)Plasticity index : Ip
Fine fraction content : FC(%)
D10 (mm)
Volcanic ash
D50 (mm)Plasticity index : Ip
Fine fraction content : FC(%)
D10 (mm)Silt
D50 (mm)Plasticity index : Ip
Fine fraction content : FC(%)
D10 (mm)
Silt mixing Sandy gravel
D50 (mm)Plasticity index : Ip

●Boring Point (existing)●Boring Point (present)

Geologic column
Depth (m)●Point B

N-valueSilt mixing
gravelSand mixinggravel

sea
Point C ●Sandy gravel

Silty sand

Point A

●Sandy siltSandy clay
Volcanicash

Point D

●0Fig. 1

50 100 (m)Sand mixing
clay

Soil investigation point at Kaminokae
Sandy gravel

The strata consist of six layers of which the soil test
results are shown in Table 1. The geologic column and thedistribution of N value of point A are shown in Fig. 2.
In addition, frozen undisturbed samples were taken in thelayers at point A to perform cyclic triaxial compression
tests and to examine the possibility of liquefaction- 298 -Bedrocklog(PointFig.2Fig. 2Boring
Boringlog (PointA)A)

13.4750.02384.2969
9.3
28.8
0.046
0.129
84.4
0.001
0.013725.15
38.7
0.00420.109696.2
0.001
0.004928.25
22.4
0.00781.48288.35

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

Fig. 3 shows the cross section and strata profile for

Table 2.

the analytical model. Three layers subjected to theliquefaction strength test are shown with shadow.

Fig. 3Stratum of the ground

Element simulations were carried out based onliquefaction resistance curve. We found a fitting curves,and determined analysis parameters. Fig. 4 shows the test
result of liquefaction strength and fitting curve. Table 2
shows analysis parameters of three layers obtained by

List of parameters
Sand Silt mixing Sandy gravel

Dry density(g/cm3)
ρd
1.423
Wet density(g/cm3)
ρt
1.8377
Void ratio
e0.9088
degree of saturation(%)
Sr
87.1
specific gravity of soil particle
Gs
2.7162
Wet unitweight(KN/m3)
γt18.0093
initial void ratio
e01.0533
N valueN
13.05
Poisson’s ratio
ν0.3251
velocity of S-wave(m/s)
Vs 188.3476
effective overburden pressure(KN/m2) σv’
161.5
angle of shear resistance(°)φ’
36.2216SINφ’
0.5909coefficient of earth pressure at rest
K00.4816
compression index
λ0.0024
expansion index
Ｋ0.0002
overconsolidation ratio
OCR*
1Curing function 1
B0*
1390
Curing function 2
B1*
10Curing function 3
Cf0
plastic strain
γrP＊
0.011
elastic strain
γrE＊
1.2
coefficient of dilatancy 1
D0*0.0001coefficient of dilatancy 2
n2.5
anisotropy
Cd2000

1.3735Silt
1.434

1.8761 1.9201
1.031 0.9963
9997.42.7896 2.863
18.3853 18.817
1.0472 1.029
4.968880.3429 0.3425
136.5125160
217.34 376.44
33.5697 33.6252
0.5530 0.5538
0.5218 0.5209
0.0365 0.0268
0.0036 0.0027
113178
3900
31.3
35
000
0
0.15 0.055
0.005 0.002
17.5
2000
2000

element simulations.

Fig.4

liquefaction strength

3. Effective stress analysis for the Sheet pile quay wall
The Computer Program for Liquefaction Analysis

Fig. 5

Analysis model with improvement

Table 3.

The physical properties of the steel

E(Pa)
A(m2)
I(m4)
ρ(g/cm3)
7.5
Sheet pile wall 2.10E+08 3.06E-02 8.60E-04
2.10E+08 5.80E-03 3.95E-04
7.5Counterfort
2.10E+08 1.59E-03
07.5
Tie rod

The steel sheet pilings, the counterfort and the tie rod

LIQCA was used for analyses. The analysis method is anwere modelled as beam elements. The steel sheet pile waseffective stress analysis method.
Fig. 5 shows the example of analysis model. This
structure comprised a sheet pile wall and counterfort

a VIL type, the counterfort was a steel pipe pile with Φ
550mm and a board thickness of 12mm.

connected with a tie rod at the top, which was employed

The steel sheet pile and the ground, and thein the restoration of a damaged wharf in the Akita Port due

counterfort and the ground, were connected using a joint

to the Nihonkai-Chubu earthquake in 1983.

element. The joint element was assumed that a friction

Table 3 shows the physical properties of the sheet
pile wall, the counterfort and the tie rod.

angle of 15 degrees. These joint elements considered slip
only.

- 299 -

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

The ground was assumed to be the same as Fig. 2 andFig. 3 and used plane strain elements. The penetration
depth of the sheet pile was to the center of the silt mixing
sandy gravel layer.

defined by the ratio of excess water pressure to theoverburden pressure. Even when countermeasures weretaken, it can be seen that excess pore water pressure isgenerated between the sheet pile wall and counterfort.

400
400

Ｍａｘｉｍｕｍ ａｃｃｅlｅrａｔｉｏｎ 306.5（gal)

300
300
200
100
0000

60

80

100
100

120

140-100-200-300

Fig. 6

Seismic base motion (levelⅠ)

The seismic waves profiles on the engineering
bedrock (N value : 50 or more) at Kaminokae area werebased on new assumptions in Kochi prefecture.
The magnitude of earthquake was 8.4. Fig. 6 shows theinput seismic wave used for the seismic response analysis.
Fig. 7 shows the analysis results for the model
without improvement and with improvement. “Withoutimprovement” indicates the case of the natural ground,and “with improvement” shows the case reinforced bysheet pile wall and counterfort.
Maximumhorizontal
displacements
wereapproximately 2.1m and 0.6m, respectively.
Fig. 8

Excess pore water pressure ratio

4. Centrifuge model tests for the Sheet pile quay wallFig. 9 shows the internal configuration of thecentrifuge used in the experiment. The interior of thedevice consists of a platform with a shaking table, rotating
spindle, rotating arm, counterweight and emergency brake.
Table 4 shows the basic specifications of the centrifuge.

Fig. 7

Horizontal displacement

Fig.8 shows the ratio of excess pore water pressure
without improvement and with improvement. The ratio is- 300 -Fig. 9

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

Table 4.

pore water pressures did not increase to overburden

Centrifuge specifications

Effective radius (mm)1925

Depth (mm)Vibration table of dimensions (mm)1700
L550×B150
L450×B150×H300
L450×B139×H355
200
30
30
1450 channels
30 channels

Experiment container size (mm)M aximum acceleration （G)M aximum frequency (Hz)M aximum displacement (mm)Power of the drive motor (KW)
M easuring Switch box
devicePressure sensor connector

pressure level. Therefore, these measuring points were notcompletely liquefied.

Fig. 11 Photographs after the experimentFig. 10 Experimental model (Model scale)

No.97

P314124.1. Liquefaction experiment by centrifuge

10In this research, liquefaction experiment is carriedout by using the centrifuge. A model with a scale of 1/40

86
401

2

were conducted with a centrifugal force field of 40 G. Fig.
10 shows the experiment model and the position of eachsensor.
The backfill soil of the sheet pile was made with
Toyoura sand with a relative density of 70%.At that time,

which is 40 times more viscous than water. The
counterforts were installed at intervals of 25 mm (1 m inactual size).

012

the real structure), and the deformation of the pile wascontrolled and the countermeasure effect was able to beconfirmed.

36462
60
58
56
54
52

4

54

545P10pile wall surface was about 2 mm (about 8 cm in terms of5No.95

123No.94

Fig. 11 shows photographs after the experiment incase of countermeasure work. Displacement of the sheet

4P2312927252321191715

the void ratio is 0.72 and the saturated density is 1.95 g /m 3. The pore water was saturated with methylcellulose,

3No.96of the analytical model was prepared and experiments

P466646260
5856540123Time (s)4.2. Pore water pressure response
Time histories of excess pore water pressure areshown in Fig.12. From the results, the upper part of excess- 301 -Fig. 12 Excess pore water pressure (Measured value)Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

Table 5.

Pore water pressure and Overburden pressure

Table 6. Acceleration Response

Measured

Pore waterOverburdenpressure (kPa) pressure (kPa)

P3
P2
P1
P4

13.2
30.0
62.5
64.8

values (m/s )Actual scale(gal)

80.5
70.7
53.8
20.1

201.3
176.9
134.5
67.8

2

16.8
33.7
61.7
56.3

a3
a2
a1
Input

Table 5 shows the relationship between the porepressure of p2 and p3 did not increase to the overburden

5．Concluding remarks
The following conclusion were obtained ;As a seismic reinforcement method for fishing portpressure level. But, the pore water pressure of p1 and p4

quay walls, the countermeasure method by sheet pile andincreased to the overburden pressure.

counterfort is effective.

water pressure and overburden pressure. The pore water

The countermeasure method using sheet pile and4.3. Acceleration response
Time histories of acceleration responses are shown incounterfort can be verified by seismic response analysis

Fig.13. Accelerations have amplified from the input

test.

method by effective stress method and centrifuge model

acceleration. Table 6 shows measured values of

The countermeasure method using sheet pile andacceleration responses and actual conversion values. It cancounterfort is highly effective in suppressing deformation

be seen that the input wave is amplified as it is transmitted

against earthquake. It is necessary to further investigate

to the upper layer.
From these results, it became clear that this method
has problems with dissipation of pore water pressure andamplification of seismic waves.

the dissipation of pore water pressure and thea3
100
50
0-50

0

1

2

3

4

5674

567-100

a2
100
50
0-50

012

3-100

a1
100
50
0024

68-50
-100

Input earthquake motion
500-5002468Time (s)Fig.13

amplification of seismic waves.
References
Japan Road Association. 2014. Specifications for
Highway bridges, Part V Seismic Design.
Kochi Prefecture, Oceanic Service Fishing Port Section.
2005. Tsunami countermeasure basic policy infishing village. Kochi Prefecture.
Ministry of Transport, Ports and Harbors Bureau. 1997.
Liquefaction measures handbook of minings, pp. 6669.
Okabayashi, K., Tagaya, K., Takeuch, T. and Ono, M.
2004. Study on disaster prediction and tsunami
refuge route to Nankai Earthquake, 14th (2004) Int.
Offshore and Polar Eng Conf., Toulon, France,ISOPE, Vol 3, pp. 733739.
Okabayashi, K., Tagaya, K. & Hayashi, Y. 2008. Study on
Earthquake Resistant Reinforcement of Existing
Quay in Fishing Port to Nankai Earthquake.
Proceedings of The Eighteenth ISOPE Conference,
pp.39-44.
Okabayashi. K, Doi. S, Tokuhisa. K, Ogawa. N andIshihara. Y. 2014. Fundamental Study on
Reinforcement of Existent Fishery Wharf by Press-in
Pile. Press-in Engineering, Proceedings of 4th IPA
International Workshop in Viet Nam.

Acceleration response (Measured value)- 302 -