Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, Japan

EARTHQUAKE DAMAGE INVESTIGATIONOF GRAVITY-TYPE QUAY WALLSIN IBARAKI PORTHidenori TAKAHASHI1, Terumi OOHASHI2 and Hidenori ENDOH31Head of Section, Yokohama Port and Airport Technology Investigation Office,Kanto Regional Development Bureau, Ministry of Land, Infrastructure,
Transport and Tourism, Yokohama, Japan, takahashi-h83ab@pa.ktr.mlit.go.jp
2Senior Staff, Yokohama Port and Airport Technology Investigation Office,Kanto Regional Development Bureau, Ministry of Land, Infrastructure,
Transport and Tourism, Yokohama, Japan, oohashi-t83ab@pa.ktr.mlit.go.jp
3Senior Staff, Kashima Port and Airport Construction Office, Kanto Regional
Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism,
Kashima, Japan, endou-h2cq@pa.ktr.mlit.go.jp

ABSTRACT: One of the most common used types of quay walls in Japan is gravity typewith concrete caissons. A number of gravity-type quay walls have been constructed inIbaraki Prefecture where huge ground motion occurred in the Great East Japan
Earthquake of March 11, 2011. This paper reports on damage to gravity-type quay wallsin the Port of Hitachinaka, which serves as a freight transport hub for the northern Kanto
region.
Key Words: Gravity-type quay walls, gantry cranes, coarse-grained rock waste, steel pilefoundation, strong motion

INTRODUCTION
One of the most common used types of quay walls in Japan is gravity type with concrete caissons. A
number of gravity-type quay walls have been constructed in Ibaraki Prefecture where huge groundmotion occurred in the Great East Japan Earthquake of March 11, 2011. The northern wharf area in thePort of Hitachinaka has two types of deep-water public quay walls for water depths of 12 m and 14 m.
The port serves as a freight transport hub for the northern Kanto region and has large gantry cranes at
the top of the quay walls to handle container cargo. The walls were constructed on the surface of a stiff
sandy stratum and backfilled with coarse-grained rock waste to prevent liquefaction. The seaward
foundations of the gantry cranes are installed on the caisson part, and the landward foundations aremounted in the top of steel piles.
The acceleration amplitude in the earthquake reached at least 5.6 m/s2 (2E-waves on theengineering seismic base layer). Some damage was caused to the northern wharf area quay walls as aresult of the strong motion, including subsidence in the backfilled ground. The caisson part of thewalls was displaced seaward by up to 56 cm, and the residual relative displacement between the687

seaward and landward crane foundations resulted in derailment damage to the crane wheels. However,the quay walls were not completely destroyed because the non-liquefiable soil material preventedliquefaction in the backfill ground. This paper reports on damage to these gravity-type quay walls in
the Port of Hitachinaka.

SYNOPSIS OF QUAY WALLS IN HITACHINAKA PORT
This chapter gives a synopsis of the Port of Hitachinaka in Ibaraki Prefecture and discusses thecross-section surface of the gravity-type quay walls.
Location of Hitachinaka Port and plane arrangement of quay walls
Figure 1 shows the location of the Port of Hitachinaka in Ibaraki Prefecture and the quay walls
examined in this study. Hitachinaka is near the epicentral area, and experienced considerable damage
in the earthquake. The plane arrangement of the quay walls in the northern wharf area is also shown inFig. 2. These walls supported operations at one of the busiest port facilities in the northern Kanto
region until the earthquake occurred. They are equipped with large gantry cranes to handle container
cargo.

Quay walls examined in study
Hitachinaka PortN

Center breakwater

Zone for port facilities
Public wharf

NNorth breakwater

Fig. 1 Location of the Port of Hitachinaka in Ibaraki Prefecture-14 m deep
-12 m (I) deep
-12 m (II) deep

Industrial siteWharf area

Fig. 2 Plane arrangement of quay walls in the northern wharf area

688

Cross-section of gravity-type quay walls
Figure 3 shows a cross-section of the gravity-type quay walls investigated in the study, which wasintended to clarify damage to two walls for water depths of 12 m and 14 m with the same structure
built using gravity-type caissons.
The walls were constructed on the surface of a stiff sandy stratum and backfilled withcoarse-grained rock waste instead of the sandy and/or silty soil usually used as backfill material. Rockwaste has the advantage of providing liquefaction resistance and reducing the earth pressure forcaissons. The use of this coarse-grained rock waste was a specific feature of these quay walls. The
seaward foundations of the gantry cranes are caisson-mounted, and the landward foundations are steel
pile-mounted.

(a) -12 m (II) deep quay wall(b) -12 m (I) and -14 m deep quay walls
Fig. 3 Cross-section of gravity-type quay walls in the northern wharf area

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GROUND MATERIAL PROPERTIESThis chapter outlines the on-site ground strength as measured in SPT testing and the properties of thecoarse-grained rock waste.
Ground conditions based on field survey
A standard penetration test (SPT) was conducted at the site to investigate strength distribution in thebackfill ground consisting of coarse-grained rock waste. The N-values found from this test are shownin Fig. 4, which includes the N-values of sand as calculated using the method defined in the Japanesetechnical standards for port and harbor facilities (OCDI, 2009). It can be seen that the N-value of rockwaste rose with increased depth, and that the values for the original ground were markedly larger thanthose of rock waste. The stiff sandy stratum was responsible for the large N-values of the originalground. Comparison of the N-values shows that the figure for sand (calculated as  = 34°) was quite
similar to that for rock waste.

N-value from standard penetration test
01020304050

Depth from ground surface (m)0Surface soil

-5-10
Coarse-grained rock waste-15 = 38°-20-25

 = 30° = 34°

Original groundFig. 4 SPT N-values in backfill ground of -14 m deep quay walls

Properties of coarse-grained rock waste
The coarse-grained metamorphic rock waste used in construction at the Port of Hitachinaka was minedin a mountainous area of Hitachi City in Ibaraki Prefecture, and its technical properties aresummarized in Table 1. The unit weight of the waste was similar to that of the soil type normally usedas backfill material.
Table 1 Technical properties of coarse-grained rock waste
Maximum grain size, Dmax
Average grain size, D50
Uniformity coefficient, Uc
Unit weight, sat
Compressive strength of original rock690

300 mm
164 mm3520.4 kN/m2
117.2 N/mm2

The grain size distribution of the rock waste used is shown in Fig. 5, which includes the typicalrange in which soil is known to liquefy readily (CDIT, 1997). The rock waste particles were large
enough to non-liquefy due to the high permeability.

Percentage finer by weight (%)

10080

Potential liquefaction
60
40
2000.001

0.01

0.1

1

10100

Particle size (mm)Fig. 5 Grain size distribution of rock waste

As the coarse-grained rock waste used in construction at the port was not tested to determine its
shear strength, Fig. 6 shows the shear strength value for a similar type of weathered andesite rockwaste mined in Hachinohe City, Aomori Prefecture. The figure shows the stress-strain curves obtained
from consolidated-drained (CD) triaxial shear testing and the relationship between volumetric strain
and shear strain. It can be seen that the initial stiffness was relatively low, and that the shear strain at
the peak strength was high. In addition, only negative dilatancy can be seen within 15% shear strain.
These characteristics can be attributed to the coarseness of the particles and the relatively low strengthof soil particles. This negative dilatancy could result in significant subsidence if the ground is shearedby earthquake motion.

-40

Mean effective stress2100 kN/m
2200 kN/m
2400 kN/m
2600 kN/m

15-30

10-20

5-10

00-5

Volumetric strain  v (%)

Principal stress difference ( 1 - 3 )

20

100

510Axial strain  a (%)

15Fig. 6 Results of CD triaxial shear tests of coarse-grained rock waste691EARTHQUAKE MOTION IN HITACHINAKA PORT

2Acceleration (m/s )As the strong-motion seismograph in the Port of Hitachinaka was destroyed by the tsunami, no groundmotion waveform data are available. Accordingly, the waveform was simulated and recreated based onother waveforms recorded in the region (Hata et al., 2011; Nozu and Nagao, 2005). Figure 7 shows thestrong motion, which was calculated as a 2E-wave on the engineering seismic base layer. According tothe waveform, the acceleration amplitude reached at least 5.6 m/s2.

NS Wave

40-42Acceleration (m/s )010203040506070Time (sec)8090100110120EW Wave

40-4010203040506070Time (sec)8090100110120(a) Ground motion waveform

2Fourier spectrum (m/s * sec)

10642

164
20.1
64NS Wave
EW Wave20.01 2345 6 7 892345 6 7 89

1Frequency (Hz)10(b) Fourier spectrum of ground motion
Fig. 7 Simulated and recreated earthquake motion

DAMAGE APPEARANCE
Photo 1 shows several instances of damage observed at the -14 m deep quay wall. The seaward
caisson displacement was up to 56 cm, as shown in Photo 1 (a), and the different displacements of692

each caisson created a concave-convex quay wall surface. This displacement also resulted insubsidence of at least 113 cm in the backfilled ground, as shown in Photo 1 (b). The residual relative
displacement between the seaward and landward crane foundations resulted in derailment damage tothe crane wheels, as shown in Photo 1 (c). However, the quay walls were not completely destroyed
because the non-liquefiable soil material prevented liquefaction in the backfill ground.

Displacement(a) Seaward displacement of caissons

Difference in level(133 cm)
LandwardSeaward(b) Subsidence in backfilled ground

Derailment(c) Derailment of crane wheels
Photo 1 Damage of quay walls

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DEFORMATION OF QUAY WALLS

Horizontal displacement (m)Horizontal displacement (m)The horizontal displacements of the caissons as measured in an on-site survey are shown in Fig. 8, in
which negative values represent seaward displacement. In both quay walls, most of the caissons
moved seaward except for those near the edge of a reclaimed area. The maximum horizontal
displacement was 56 cm for the -14 m deep quay wall. The edge of the reclaimed area corresponding
to the corner of the quay walls exhibited behavior different from that of the standard area.

Distance from edge of port berth (m)050

100150-12 m deep quay walls-12 m (II) deep

0.5

200

250

-12 m (I) deep
Position of No.16

0.0-0.5

Distance from edge of port berth (m)
00.5
0.050

100150200250-14 m deep quay walls
Position of No.10

Edge of reclaimed area-0.5*Negative value represents seaward displacement.

Fig. 8 Horizontal displacement of caissons
Figure 9 shows pre- and post-earthquake cross-sections of the -14 m deep quay wall. It illustrates
only ground surface and caisson displacement because only measurement of surface displacement wasconducted in the field. It can be seen that the incremental volume generated by caisson seaward
movement was about 10.4 m3, and the decremental volume generated by backfill ground subsidence
was about 25.0 m3. The volume balance resulting from these two values is 14.6 m3, indicating that theaverage volumetric strain of the backfill ground was not large.

Fig. 9 Cross-section of pre- and post-earthquake694

DEFORMATION OF STEEL PILE FOUNDATIONSThere is currently no established method for measuring the displacement of an inclined or bent steel
pile. In this study, steel pile displacement was measured using the method shown in Fig. 10. First, aninclined pipe with relatively low stiffness was fitted into the steel pile with the aid of spacers. Then, aborehole inclinometer was inserted into the inclined pipe to measure its inclination. Finally, thehorizontal displacement of the inclined pipe was calculated from the angle of integration. Its
displacement was considered to be almost the same as that of the steel pile.

Steel pile
Borehole inclinometerSpacerIncline pipe
Inclinepipe
Inclinepipe

Fig. 10 Method for measuring horizontal displacement of steel pile foundation

The horizontal displacements of two representative steel piles are shown in Fig. 11, whichindicates that the seaward displacements of the pile tops were 0.52 m and 0.63 m, and that the piles
bent seaward from deep to shallow parts. The radius of the curvature calculated from thedisplacements shows that these piles reached their yield condition, indicating the need forreplacement.

Horizontal displacement (m)Depth from top of steel pile (m)

0.0
0

0.2

0.4

0.6

0.8

1.0

-5

-10-15

Steel pile No.10
Steel pile No.16-20

Fig. 11 Horizontal displacement of steel piles695CONCLUSIONSThis paper reports on damage to gravity-type quay walls in the Port of Hitachinaka. Quay walls
subjected to strong earthquake motion in the northern wharf area experienced damage, includingbackfilled-ground subsidence and caisson displacement. The horizontal displacement of the walls
caused the steel piles supporting the cranes to yield, and the residual relative displacement between theseaward and landward crane foundations resulted in derailment damage to the crane wheels. However,the quay walls were not completely destroyed because the non-liquefiable soil material used(coarse-grained rock waste) did not liquefy in the backfill ground. The volumetric strain of this rockwaste was limited.
Restoration construction based on the previous structures is currently under way. Additionally, aseries of shaking model tests and numerical analyses are planned to elucidate the mechanism ofdynamic ground behavior and the damage process. In the near future, these surveys are expected toprovide more information on the deformation behavior of gravity-type quay walls in the Port ofHitachinaka.

ACKNOWLEDGMENTS
The authors would like to express their gratitude to all who contributed to the study, particularly Dr.
Nozu of the Port and Airport Research Institute for his help with the simulation and recreation ofstrong motion in the Port of Hitachinaka; Mr. Hattori and Ms. Sugiura of the Yokohama Port andAirport Technology Investigation Office for supporting the authors in producing the paper’s figures;and the Kashima Port and Airport Construction Office for its enormous contribution to the fieldsurveys.

REFERENCES
Overseas Coastal Area Development Institute of Japan, OCDI (2009). “Technical standards andcommentaries for port and harbour facilities in Japan.” MLIT, NILIM, and PARI, pp.
228-229.
Coastal Development Institute of Technology of Japan, CDIT (1997). “Handbook on liquefaction
remediation of reclaimed land -revised edition-.” CDIT, p. 116. (in Japanese)
Hata, Y., Nozu, A. and Ichii, K. (2011). “A practical method to estimate strong ground motions
after an earthquake, based on site specific amplification and phase characteristics.”
Bulletin of the Seismological Society of America, Vol. 101, No. 2, pp. 688-700.
Nozu, A. and Nagao, T. (2005). “Site amplification factors for strong-motion sites in Japan
based on spectral inversion technique.” Technical Note of the Port and Airport ResearchInstitute, No. 1112, 56p.

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