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

SEVERAL FEATURES OF LIQUEFACTION-INDUCEDDAMAGE TO HOUSES AND BURIED LIFELINESDURING THE 2011 GREAT EAST JAPAN
EARTHQUAKE
Susumu YASUDA1 and Keisuke ISHIKAWA2
1

Professor, Department of Civil and Environmental Engineering, Tokyo Denki University,
Saitama, Japan, yasuda@g.dendai.ac.jp
2
Assistant, Department of Civil and Environmental Engineering, Tokyo Denki University,
Saitama, Japan, ishikawa@g.dendai.ac.jp

ABSTRACT: The 2011 Great East Japan earthquake caused severe liquefaction in
Tohoku and Kanto districts. About 27,000 timber houses, a lot of buried sewage pipes
and roads were damaged due to liquefaction. In Tokyo Bay area, the very long duration of
the main shock and an aftershock 29 minutes later probably induced the severeliquefaction. Sidewalks and alleys buckled at several sites, probably due to a kind ofsloshing of liquefied ground. Moreover, much sand boiled from the ground and the groundsubsided significantly because the liquefied soils were very fine.
Key Words: Great East Japan earthquake, liquefaction, house, sewage pipe, road

INTRODUCTION
The 2011 Great East Japan Earthquake, with a magnitude of Mw=9.0 occurred in the Pacific Ocean
about 130 km off the northeast coast of Japan’s main island on March 11, 2011. Liquefaction occurredin a wide area of reclaimed land along Tokyo Bay, though the epicentral distance was very large, about
380 to 400 km. Much land has been reclaimed in the Tokyo Bay area since the seventeenth century.
Liquefaction has been induced during past earthquakes, such as 1923 Kanto Earthquake and 1987
Chibake-toho-oki Earthquake. However, the Great East Japan Earthquake is the first on record to causeliquefaction in such a wide area and to severely damage houses, lifelines and roads. In this paper, theauthors focus on the liquefaction-induced damage in Tokyo Bay area.

INVESTIGATION OF LIQUEFIED SITES
The authors started to investigate Tokyo Bay area on the next day from the earthquake because all train
in Tokyo Bay area stopped service immediately after the earthquake until the midnight of the day. In theinvestigation the roads where boiled sands were observed and not observed, were marked on maps asshown in Figures 1. The zones surround by red lines were judged to be liquefied, but. note is necessary825Figure 1 Method to judge liquefied and non-liquefied zone (Yasuda et al., 2011)

Funabashi
Ichikawa
Narashino

OdaibaLiquefied zones judged byauthors on May
Liquefied zones added by
JGS and MLITT on August
Delete zones by JGS and
MLITT on August

Shinkiba
Urayasu

Chiba

Figure 2 Liquefied area from Odaiba in Tokyo to Chiba City (Joint research by Kanto Regional
Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism and JGS)
that some small districts in the zones did not liquefy because their grounds had been improved by sandcompaction method or other methods mentioned later. Thus about ten days were necessary to investigate
the whole area from Odaiba in Tokyo to Chiba City through Urayasu, Ichikawa and Narashino Cities. A
tentative map of liquefied zones was drawn based on this first stage investigation (Yasuda and Harada,
2011).
As the liquefaction-induced damage to houses, river dikes, roads, lifelines and ports and harbors
were serious, Kanto Regional Development Bureau of the Ministry of Land, Infrastructure, Transport
and Tourism, intended to make joint research with JGS to identify liquefied sites. Figure 2 is the map ofliquefied zones thus estimated which is slightly modified from the tentative map.

SOIL CONDITION IN LIQUEFIED AREA
As demonstrate in Figure 2, severely liquefied area by the earthquake was from Shinkiba in Tokyo to
Chiba City through Urayasu, Ichikawa, Funabashi and Narashino Cities in Chiba Prefecture. The
reclaimed lands in this area were constructed after 1966. In the reclamation work dredged soils werefilled from the bottom of sea to the height of about sea level. Then the filled surface was covered withhill sands. Figure 3 draws the process of the dredging work. The soils of sea bottom were excavated by acutter, exhausted with water by a pump, transported by a convey pipe then discharged from the exit of826

Pump dredger
Discharge pipe
Floating pipe

Sea level
CutterPump

Sea bottom

Discharge
opening

Distributing pipe
Sea
wall

Reclaimed soil

Figure 3 Process of dredging work

Figure 4 Estimated brief soil cross sections
the pipe. As the dredged soils contain much water, coarse soil grains and fine soil grains are apt todeposit near the exit and far from the exit, respectively. Moreover the position of the exit moves tovarious positions, resulting in very non homogeneous strata. After filling with the dredged soils andcovered by the hill sands, no soil improvement works were treated except several special areas where
sand compaction piles or gravel drain piles and other methods were applied to prevent liquefaction.
As three sets of data base had been published by JGS, Chiba Prefecture and Tokyo Metropolitan in
the liquefied area, the authors estimated brief soil cross sections along 11 lines which are perpendicular
to the shore lines based on these data. Figure 4 illustrate the estimated soil cross sections along a line in
Urayasu 3-3’ together with the zones where sand boils were observed. The zones where sand boils wereobserved are exactly coincided with the area of reclaimed land which is the sea side from old sea wall. In
the reclaimed zone, a filled layer with mainly hill sand (B) and a filled layer by dredged sandy soil (F)with low SPT N-values of 2 to 8 are deposited with a thickness of 6 to 9 m. An alluvial sand layer (AS)with SPT N-values of 10 to 20 underlay with a thickness of 4 to 8 m. A very soft alluvial clay layer (Ac)is deposited under the AS layer with a thickness of 10 to 40 m, by increasing the thickness towards sea.
Diluvial dense sandy layer (Ds) with SPT N-value more than 50 underlay. Water table is shallow as GL-0.5 m to -3 m, by decreasing the depth towards sea. On the contrary, in the zone where sand boil was notobserved, AS layer deposited from ground surface. Therefore it can be estimated that the As layer
basically did not liquefy by the 2011 Great East Japan earthquake though some loose part might liquefy
in the reclaimed land, and that some part of the dredged sandy soil under water table might liquefied.
Composition of soil layers is similar in other 10 soil cross sections, though thickness of each layer isdifferent.
A technical committee organized by Urayasu City Government and chaired Prof. K. Ishihara carried

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Numberof samples
データ数

500
400
300
200

μ‐σ

200

100

0

0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100
FC (%)

5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50
N1
350

250

μ

μ+σ

平均値μ=12.9 標準偏差σ=9.09(3)
Alluvial
sands
サンプル数N=1160
Average N1=12.9

200
150
100
50

平均値μ=30.9 標準偏差σ=25.3(4)
Alluvial サンプル数N=498
sands
Average FC=30.9%

300

Number データ数
of samples

μ‐σ

μ+σ

μ

150

0

350

Numberデータ数
of samples

250

50

300

標準偏差σ=30.4(2) Dredgedサンプル数N=410
soils
Average FC=43.8%

300

100

0-5

平均値μ=43.8

標準偏差σ=6.33(1) Dredgedサンプル数N=993
soils
Average N1=5.46

250
200

μ‐σ

μ

μ+σ

150
100
50
0

0
0-5

0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100
FC (%)

5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50
N1

N1=170N/(σv’+70), σv’：Effective overburden pressure (kN/m2)

Figure 5 Frequency distributions of N1 and Fc for dredged
soils and alluvial sands (Quoted from the researchmaterial by the Technical Committee organized by
Urayasu City)

0.40～0.45
0.35～0.40
0.30～0.35
0.25～0.30
024
Number of samples(1) Dredged soils

Shear stress ratio to causeliquefaction RL(NL=20, DA=5%)

平均値μ=5.46

μ+σ

Numberデータ数
of samples

μ600

Shear stress ratio to causeliquefaction RL(NL=20, DA=5%)

350

700

0.40～0.45
0.35～0.40
0.30～0.35
0.25～0.30
0

2

4

6

Number of samples(2) Alluvial sands

Figure 6 Frequency distributionsof shear stress ratio to causeliquefactionout detailed soil investigations in Summer by boring, SPT, CPT, PS logging, undisturbed sampling,
cyclic triaxial tests and others, and reported valuable data in December 2011. Frequency distributions ofnormalized SPT N-values, N1 and fines content, Fc of the F layer and the AS layer are compared in
Figures 5 (1) to (4). Fines content of the F layer are very scattered and greater than the fines content of
the AS layer, though the F layer was essentially taken from the As layer. This difference must be
attributed to the lack of the alluvial sandy soils for the reclamation work. As the dredged zones werelocated just the top of a delta formed by Edo River, sandy soils were not enough for the filling, thensome alluvial clays had to be excavated and mixed with the alluvial sandy soils. Average value of thefines content of the F layer is extremely high as 43.8 %. However, plasticity indexes, IP are not highthough their fines content are large. N1 of the F layer is apparently lower than that of the AS layer.
Undisturbed samples were taken at nine sites to obtain cyclic shear strength and shear modulus.
Frequency distributions of shear stress ratio to cause liquefaction in 20 cycles tested by cyclic triaxial
tests, RL (NL=20, DA=5%) for the F and the AS layers are shown in Figure 6. Dominant RL values for the
F layer and the AS layer are 0.25 to 0.30 and 0.30 to 0.40, respectively though the data are very scatter in
the F layer. Therefore it can be said the soils in the F layer are more liquefiable than those in the AS layer.

PROCESS OF LIQUEFACTION
As the earthquake occurred at 14:46 in the afternoon on Friday, many important photos and movies weretaken at many sites along Tokyo Bay to study the process and mechanism of liquefaction. Among them aseries of photos taken by Mr. Katsunori Ogawa just after the earthquake at Maihama 3-chome in
Urayasu City is introduced in Photos 1 (1) to 1 (4):<<<Shake due to main shock started at 14:47 in Urayasu>>>
A <14:56>: Spew out of muddy water started in northeast direction. It took several minutes to start theboiling after the settle of the main shock.
B <15:01>: Boiled muddy water gradually spread and covered the road.
<<<A strong aftershock hit Urayasu at 15:16>>>
C <15:21>: The southwest road covered completely with muddy water. Water pipes look like to break.

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Photo 1 Sequential photos taken by Mr. K. Ogawa

Figure 7 Questionnaires to inhabitants in Irifune
D <15:22>: Many houses settled and tilted and cars submerged in the boiled muddy water.
The authors sent out questionnaires to about 30 inhabitants in Irifune district which is also located in
Urayasu City to ask the timing of boiling and height of boiled muddy water. Answers are summarized in
Figure 7. About 1/3 persons observed the boiling of muddy water immediately after the main shock,however another 1/3 persons recognized the spout of muddy water 5 to 9 minutes after the main shock.
Other persons found the muddy water at different timing. Height of the muddy water was not high as829

mainly less than 9 cm after the main shock. About 2/3 persons mentioned that the boiling of muddy
water continued up to the aftershock, and about 3/4 persons watched covered water until aftershock. On
the contrary, about 3/4 persons observed spew out of muddy water just after the aftershock and theheight of the water was apparently greater than the height after the main shock. This means the boilingaccelerated due to the aftershock and more severe liquefaction occurred during aftershock at some sites.
Question on the timing of the settlement of houses must be difficult to answer for inhabitants, however,a 1/3 persons and another 1/3 persons answered that the settlement of their houses was zero and 10 to 19
cm, respectively after the main shock. And, many inhabitants recognized the settlement on the next day.
According to the hearing in Imagawa district some inhabitants testified boiling did not occur duringmain shock but occurred during aftershock.

EFFECT OF LONG DURATION OF SHAKING ON LIQUEFACTION
Figure 8 shows ground surface accelerations during the main shock and the aftershock. Surface
accelerations were not high as around 160 cm/s2 to 230 cm/s2 though severe liquefaction occurred. The
accelerograph recorded at K-NET Inage in Chiba where actually boiled sand was observed, is very
important because liquefied time can be judged from the recorded waves. Figure 9 shows theaccelerograph at Inage together with that at K-NET Urayasu which was recorded on the ground in whereliquefaction did not occur. Both records started almost same time; 14:46:16 at Inage and 14:46:15 at
Urayasu. In Urayasu’s wave frequency did not change drastically after the peak acceleration which
induced at about 118 sec. (14:48:13). On the contrary frequency changed to low value after two peaks at
120 sec. (14:48:16) and 126 sec. (14:48:22). Therefore it can be judged liquefaction occurred at aroundFigure 8 Comparison of accelerations during main and aftershocks by K-NET

Figure 9 Comparison of accelerographs recorded at K-NET Inage and Urayasu

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14:48:16 to 14:48:22 at K-NET Inage. This means many cycles of shear stress, say around 20 cycles
from 110 sec. might cause liquefaction at K-NET Inage site. And it must be noted shaking still continued
for long time after the occurrence of liquefaction. By referring to the accelerograph at K-NET Urayasu,
shake of the ground at Inage continued for about 3 minutes after liquefied.
One more impact to the ground must be the shaking during the aftershock. Peak accelerations during
the aftershock were almost a half of those during the main shock in Tokyo Bay area as shown in Figure
8. Even though, as mentioned above, boiling occurred after the aftershock at some site. Therefore, major
reason of the severe liquefaction must be the effect of long duration of shaking during main shock andan aftershock. The authors tried to conduct cyclic torsional shear tests and some simple analyses toevaluate the effect of the long shaking on the occurrence of liquefaction. Two types of shear wave wereapplied to specimen, sine wave of 20 cycles and the seismic wave recorded during main shock and after
shock at Urayasu K-NET. In case of seismic wave, excess pore water pressure increased gradually withshear stress as illustrate in Figure 10. Then, relationships between stress ratio R (τd/σ’) for sine wave
or Rmax (τmax/σ’) for seismic wave and residual excess pore water pressure u/σc’ are plotted in Figure

Figure 10 Time histories of shear stress, shear
strain and excess pore water pressure

Figure 12 Analyzed FL at Imagawa in
Urayasu City

Figure 11 Relationship between shear
stress ratio and excess porewater pressure

Figure 13 Effect of CW on PL831

11. As R=0.27 for u/σc’=1.0 and Rmax=0.31 for u/σc’=1.0, the correction factor Cw by JRA standard(2002) becomes 0.82. Then safety factor against liquefaction FL and liquefaction potential PL were
evaluated for every boring data used for the estimation of 11 brief soil cross section, under the conditionsof Cw=0.82 and 1.0. In the estimation, RL was estimated from SPT N-values and Fc, by using the
proposed formula by the technical committee of Urayasu City. Figure 12 shows evaluated FL values fora boring data in Urayasu where liquefaction occurred. If the Cw is assumed as 1.0, all FL are estimatedgreater than 1.0 whereas FL are less than if Cw is assumed as 0.82. Figure 13 compares PL for all boringdata under the assumption of Cw=0.82 and Cw=1.0. If Cw=0.82, PL for liquefied sites are calculated as
greater than about 10 and severity of liquefaction can be demonstrated.

SETTLEMENT AND TILTING OF HOUSESAccording to the result of totaling by the Ministry of Land, Infrastructure, Transport and Tourism, about
27,000 houses were damaged due to liquefaction as shown in Table 1. Photos 2 (1) and 1 (2) show adamaged house taken from outside and inside, respectively. The house settled and tilted about 40/1,000.
In the heavily tilted houses, inhabitants feel giddy and nausea and difficult to live in their houses after
the earthquake. However damaged houses due to liquefaction had been judged as partial collapse or
injured only during past earthquakes because of no damage to walls and windows, though it has been
desired both settlement and inclination must be considered in the judge.

Table 1 Number of damaged
housesduetoliquefaction (by the
Ministry of Land,
Infrastructure,
Transport and Tourism
Prefecture

Number ofdamaged houses

Iwate

3

Miyagi

140

Fukushima

1,043

Ibaraki

6,751

Gunma

1

Saitama

175

Chiba

18,674

Tokyo

56

Kanagawa

71

Total

(1) Outside of the tilted house

26,914(2) Outside of the tilted house

Photo 2 Severely settled and tilted house in
Urayasu City

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Table 2 New evaluation standard forthe damage of houses
Grade ofdamageCompletely
destroyed
Large-scalepartially
destroyed
Partially
destroyed

Evaluation method
Inclination
Settlement
Floor to 1m
More thanupper than
1/20
floor
25
cm
1/60
to upper thanfooting to
1/20
floor
Up to 25 cm
1/100
toupper than
1/60
footing

Table 3 Numbers of damaged houses in Urayasu Cityby old and new standard (Urayasu City)
Grade of damage
Completely
destroyed
Large-scalepartially destroyed
Partially destroyed

Number of houses
New
Old standard
standard
8

18

0

1,541

33

2,121

Partially injured

7,930

5,096

No damage

1,028

1,105

Total

8,999

9,981

Figure 14 Possible effect of aftershock on the settlement of house
Then, on May, Japanese Cabinet announced new evaluation standard for the damage of houses by thetwo factors, settlement and inclination, as shown in Table 2. Numbers of damaged houses in Urayasu
City by the new standard are listed in Table 3 together with the numbers counted by old judging method(Urayasu City, 2011). Numbers of completely and partially destroyed houses increased drastically, andthe numbers of damaged houses more severe than partially destroyed enlarged to 3,680.
As mentioned above, occurrence of liquefaction must be affected by the aftershock. Not only theoccurrence of liquefaction but also the settlement and inclination must be affected by the aftershock.
Ground water table increased after the main shock and boiled muddy water covered the ground surface
until the aftershock at many sites. Then, settlement of houses is excitable during the aftershock thoughshaking amplitude was less than that during the main shock as schematically shown in Figure 14.
Many inhabitants along Tokyo Bay are facing to the serious problem how to restore the damaged
houses. Complicated problem is the re-liquefaction during aftershocks or future earthquakes. Not only
the restoration but also some countermeasure against re-liquefaction must be applied, but the problem isthe cost and the technique to treat the ground under existing structures. Then early development on
effective and economic measures against liquefaction for existing timber houses are facilitating byseveral organizations. Moreover, applicability of special measures to improve an area by decreasing
ground water table is studying.

DAMAGE OF SEWAGE PIPES AND MANHOLES DUE TO SLOSHING OF LIQUEFIEDGROUND
Miracle phenomena, heaving, buckling or thrust were observed at several footways and alleys as shownin Photo 3 at many sites in Tokyo Bay area. Some thrust might occur at the boundaries due to a kind ofsloshing of liquefied ground as schematically shown in Figure 15 (1), because shaking continued forlong time after the occurrence of liquefaction. Figure 16 shows heaved footways or alleys in Urayasu
City together with contour lines of the thickness of the F layer under the ground water table. It may besaid that the heaving occurred at the sites where the bottoms of the F layer, in other word liquefied layer,

833

Photo 3 Heaving of a footway at
Takahama, Ichikawa City

Figure 15 Two possible mechanism of heaving

Figure 16 Heaved footways or alleys in Urayasu City together with contour lines of the
thickness of the F layer under the ground water table (Contour lines are quoted
from research materials (2011))
are sloped. This implies that a kind of horizontal buckling of surface layer might occurred due to theconcentration of horizontal compressive stress as schematically shown in Figure 15 (2). However, morestudies are necessary on the mechanism of the buckling.
In sewage facilities, pipes were meander or broken, joints were pulled out and pipes were filled withmuddy water. Many manholes were sheared in horizontal direction and filled with muddy water whereas
few manholes uplifted. Though the mechanism of these unique damages is still studying, one authors’idea is illustrated in Figure 17. As mentioned above a kind of sloshing of liquefied ground might occur
due to long duration of shaking and caused thrust of roads. By the same movement of the ground, pipes
might meandered violently in horizontal direction, resulting pull out or break of joints, and eventuallyliquefied muddy water invaded into the pipes. Manholes might be sheared due to horizontal force andpressurized liquefied muddy water came into the manholes. Fortunately or unfortunately invaded
muddy water into the sewage pipes and manholes might prevent uplift.

834Percent finer by weight

Figure 17 Unique damage to sewage manholes and pipes

Grain size (mm)Tokyo Bay area

FigureChristchurch

18 Comparison of grain size
distribution curves of boiled
sands in Tokyo and Christchurch

Photo 4 Thick boiled soil observed in Chiba
City

TRAFFIC PROBLEMS DUE TO BOILED SAND AND SUBSIDENCE
Much eruption of sands and large ground subsidence occurred in the liquefied area. The maximum
thickness of the erupted sand and the maximum ground subsidence observed by the authors were about
30 cm and 50 cm, respectively. This is the first experience for the authors to see such thick deposited
boiled sand in Japan. However, one of the authors had seen similar much eruption and large subsidencein Christchurch during the main shock on September 2010 and aftershock on February 2011. Figure 18
compares grain size distribution curves of erupted soils in Christchurch during the main shock withthose in Tokyo Bay during this earthquake. Fines contents for Christchurch and Tokyo Bay are similar.
Then it is estimated that in the very fine sands, ejection of water continues for long time because of low
permeability of liquefied soils in both area. Moreover fine soil particles are easy to uplift above theground surface by the ejecting water. And the removal of the deposited soils by inhabitants accelerated
the settlement of the ground surface.
Photo 4 shows an alley covered by boiled sands. It was difficult to run on the thick deposited wet
sands by cars and bicycles. Moreover large settlement of the ground around buildings prevented to go
out from parking spaces.

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CONCLUSIONS
Severe liquefaction occurred by the 2011 Great East Japan Earthquake in Tokyo Bay area. Seismic
intensities in the liquefied zones were not high, though the liquefied ground was covered by boiled sands.
The very long duration of the main shock and an aftershock 29 minutes later should have induced thesevere liquefaction. Many houses settled substantially and tilted seriously due to liquefaction. Sewage
pipes meandered or were broken, joints were extruded from the ground, and pipes were filled withmuddy water. Many manholes were sheared horizontally and filled with muddy water, whereas few
manholes were uplifted. This remarkable damage to buried pipes and manholes might have occurred
due to a kind of sloshing of liquefied ground.

ACKNOWLEDGEMENTS
Some of the results cited in this paper are quoted from the report by the Technical Committee on
Measures against Liquefaction chaired by Prof. K. Ishihara and organized by the Urayasu City
Government. Mr. K. Ogawa provided us important photos. The authors would like to express theirsincere appreciation to them.

REFERENCES
Japan Road Association (2002). “Specification for highway bridges.”. (in Japanese).
National Research Institute for Earth Science and Disaster Prevention (NIED) “K-NET WWW
service.” Japan (http://www.k-net.bosai.go.jp/).
Research material of the technical committee organized by Urayasu City Government.
http://www.city.urayasu.chiba.jp/menu11324.html (in Japanese)
Yasuda, S. and Harada. K. (2011) “Liquefaction-induced damage in the reclaimed lands along Tokyo
Bay.” Geotechnical Engineering Magazine, JGS, Voi.59, No.7, pp.38-41, 2011.(in Japanese).
Yasuda, S., Harada, K. and Ishikawa, K. (2012). “Damage to structures in Chiba Prefecture during the2011 Tohoku-Pacific Ocean Earthquake.” Geotechnical Journal, JGS (in Japanese, in printing).

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