Journal of JSCE, Vol. 1, 181-193, 2013
Special Topic - 2011 Great East Japan Earthquake (Invited Paper)
LIQUEFACTION-INDUCED DAMAGE TO
STRUCTURES DURING THE 2011 GREAT EAST
JAPAN EARTHQUAKE
Susumu YASUDA1, Ikuo TOWHATA2, Ichiro ISHII3, Shigeru SATO4
and Taro UCHIMURA2
1Member of JSCE, Professor, Dept. of Civil and Environmental Eng., Tokyo Denki University
(Hatoyama, Hiki-gun, Saitama 350-0394, Japan)
E-mail: [email protected]
2Member of JSCE, Dept. of Civil Eng., University of Tokyo (7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan)
E-mail: [email protected], [email protected]
3Member of JSCE, Deputy Mayor, Urayasu City (1-1-1, Nekozane, Urayasu, Chiba 279-8501, Japan)
E-mail: [email protected]
4Member of JSCE, Consultant Engineer, Pacific Consultants Co., Ltd.
(6-8-1, Nishi-shinjyuku, Shinjyuku, Tokyo 163-6018, Japan)
E-mail: [email protected]
The 2011 Great East Japan Earthquake caused liquefaction in many places in the Tohoku and Kanto
regions. Because of some areas’ geomorphologic condition, liquefaction occurred in artificially reclaimed
lands along Tokyo Bay and the Pacific Ocean, filled lands on former ponds and marshes, and sites of excavation to get iron sands or gravels which had been filled. The most serious damage occurred in Urayasu
City, near Tokyo. About 85% of the Urayasu City area liquefied and wooden houses, roads and buried
pipes were damaged. However, buildings and bridges supported by piles were not damaged even though
the ground around them liquefied. In the Tohoku and Kanto regions, river dikes were damaged at about
2,100 sites, mainly because of the liquefaction of the foundation ground and/or embankments. Sewage
pipes and manholes sustained two types of damage: i) lifting due to the liquefaction of replaced fill soils,
and ii) the shear failure of manholes and disconnection of pipe joints due to the liquefaction of filled soils
and the surrounding ground. Oil tank yards, harbor structures and a tailings dam were also damaged.
Key Words : liquefaction, sandy soil, road, river dike, buried pipe
1. INTRODUCTION
Soil liquefaction during earthquakes causes severe
damage to many structures. Buildings, tanks, and
embankments settle because the soil beneath them
loses strength. Underground tanks and buried pipes
are lifted because the ground becomes like a liquid
and floats owing to buoyancy. Quay walls move
towards the sea due to increased earth pressure on
them. Piles bend by the horizontal seismic inertial
force of superstructures because their bearing capacity is reduced. Moreover, if the ground faces a waterfront or has a gentle slope, liquefaction tends to
cause it to flow, often inducing extreme damage,
such as the collapse of pile foundations.
During the 2011 Great East Japan Earthquake, soil
liquefaction occurred in the Tohoku region of
northeastern Japan and in the Kanto region sur-
rounding Tokyo because the earthquake was huge,
with a magnitude of Mw=9.0. Liquefaction occurred
in a wide area of reclaimed land along Tokyo Bay,
though the epicentral distance was very large, about
380 to 400 km. Large amounts of boiled sand, large
settlements and a kind of sloshing of liquefied
grounds were observed in the Tokyo Bay area. Many
houses, roads, lifeline facilities, and river dikes were
severely damaged by soil liquefaction1), 2). The most
seriously damaged city was Urayasu City, where
about 85% of the city area liquefied. Some port and
harbor facilities, tank yards, electric power stations
and tailings dams were also damaged in the Tohoku
and Kanto regions. However, many new bridges,
buildings, tanks, port and harbor facilities, etc. escaped damage because these structures had been
designed to withstand the effect of liquefaction. Old
structures which had not been originally designed to
withstand the effect of liquefaction but had been
repaired to prevent liquefaction-induced damage
were not damaged either. In this paper, liquefaction-induced damage to structures during the 2011
Great East Japan Earthquake is introduced by focusing on the damage in Urayasu City.
2. BRIEF HISTORY OF THE DESIGN
METHODS FOR LIQUEFACTION IN
JAPAN
In 1964, the Niigata and Alaska earthquakes inflicted huge damage on buildings, bridges and other
structures by liquefying loose sandy soils. After these
earthquakes, studies on liquefaction began to be
widely carried out using laboratory cyclic shear tests,
shaking table tests, and site investigations and analyses. Based on these studies, methods for the prediction of liquefiable layers, the design of structures
in liquefied grounds and measures to prevent liquefaction were developed. In Japan, since 1970, design
methods for liquefaction have been introduced in the
seismic design codes for port and harbor facilities,
highway bridges, railway structures, and buildings,
as shown in Table 1. Later design methods were
introduced for almost all important facilities, such as
oil tanks, LNG tanks, high-pressure tanks, water
pipes, sewage pipes and gas pipes. However, for
water and sewage facilities, these design methods
were applied only to major pipes in the early stage,
and then gradually applied to normal pipes.
Countermeasures against liquefaction have also
been developed. During the 1964 Niigata earthquake,
many oil tanks settled due to liquefaction. However,
some tanks were not damaged because their foundation ground had been compacted by vibro-flotation3).
This was the first time that the effectiveness of
ground compaction against liquefaction was recognized. After this, many other kinds of remediation
methods were developed in Japan, including sand
compaction piles and gravel drains. These remediation methods were summarized in a book by the
Japanese Geotechnical Society (JGS) in 1993 in
Japanese, which was translated into English in
19984).
Recently, almost all new structures have been designed to prevent damage due to liquefaction.
However, many structures remain which were constructed before their seismic design codes considered
liquefaction, and many small structures are still designed without consideration of the effect of liquefaction. Fig.1 summarizes the earthquakes that
caused liquefaction-induced damage to structures
from 1964 to 2011, when the Great East Japan
Earthquake occurred. As shown in Fig.1, liquefaction occurred during 25 earthquakes in those 47 years
in Japan.
During the 2011 Great East Japan Earthquake,
many wooden houses were damaged due to liquefaction, though no one died as a result. According to
the Ministry of Land, Infrastructure, Transport and
Tourism, about 27,000 houses were damaged due to
liquefaction. This large number of houses suffered
damage because no design method for liquefaction
has been introduced for wooden houses, since liquefaction-induced settlement of houses does not
cause serious problems or threats to inhabitants, such
as loss of life. Many of the buried structures and river
dikes that were damaged had been constructed before
liquefaction was considered in their seismic design
codes.
On the other hand, many structures, such as elevated bridges, buildings, high-pressure gas pipelines,
Table 1 Years when consideration of liquefaction was introduced in seismic design codes in Japan.
Design codes and standards
1994 Hokkaido‐toho‐oki Eq. 1993 Hokkaido‐nansei‐oki Eq.
Year
Design standard for port and harbour facilities
1970
Seismic design manual for highway bridges
1972
Design criteria of building foundation structures and commentaries
1974
Design standard for railway structures, foundation and retaining wall
1974
1983 Nihonkai‐chubu Eq。
2008 Iwate‐Miyagi‐nairiku Eq. 2004 Niigataken‐chuetsu Eq. hazardous materials
Guideline for remedial measures of water works facilities against earthquakes 1979
Specification of construction of tailing dams and commentary
1980
1993 Noto‐hanto Eq. Recommendation practice for LNG in-ground storage
1981
2007 Noto‐hanto Eq. Guidelines for remediation measures of sewage works facilities against 1981
earthquakes
The
Ministerial
Notification
for
Aseismic
Design
(MITI
Notification 1983
No.515,1981)
Seismic design standard of land reclamation for Agriculture (Draft)
1984
Seismic design manual for housing sites
1984
Design manual for common utility ducts
1986
Highway earthquake series, manual for soft ground remediation
1986
Technical guidelines for aseismic design of nuclear power plants
1987
Design method of high-pressure gas pipeline for liquefaction
2001
1968 Tokachi‐oki Eq. 1994 Sanriki‐haruka‐oki Eq. 2007 Niigataken‐
chuestu‐oki Eq. 1978 Miyagiken‐oki Eq. 2003 Miyagiken‐hokubu no Eq. 2000 Tottoriken
‐seibu Eq. 2011 Great East Japan Eq. 2005 Fukuokaken
‐seiho‐oki Eq. 1987 Chibaken‐toho‐oki Eq. 2009 Surugawan‐oki
No Eq. 2001 Geiyo Eq.
1993 Kushiro‐oki Eq. 2003 Tokachi‐oki Eq.
1982 Urakawa‐oki Eq. 1964 Niigata Eq
Notification specifying particulars of technical standards concerning control of 1974
1973 Nemurohanto
‐oki Eq. 1978 Izuohshima‐kinkai Eq. 1995 Hyogoken‐nambu (Kobe) Eq.
Fig.1 Sites of soil liquefaction in Japan caused by earthquakes
from 1964 to 2011.
and oil tanks, were not damaged, even though severe
soil liquefaction occurred, because these structures
had been designed to resist liquefaction damage by
incorporating pile supports or improving the foundation soil.
about 30 minutes after the earthquake. According to
several photos and videos taken after the earthquake
and before the tsunami, liquefaction may have occurred in natural ground, as well as in reclaimed land.
In higher ground unaffected by the tsunami, filled
soils at many housing lots and a tailings dam liquefied.
3. GEOMORPHOLOGICAL FEATURES
OF LIQUEFIED SITES
Liquefied sites in the Tohoku and Kanto regions
were investigated by many members of the Japan
Society for Civil Engineering (JSCE), the JGS, and
others. As the liquefaction-induced damage to
houses, river dikes, roads, and lifeline facilities was
serious, the Kanto Regional Development Bureau of
the Ministry of Land, Infrastructure, Transport and
Tourism conducted joint research with JGS to identify liquefied sites. The results of their joint research
were published on the government ministry’s website5). Fig.2 is a map of the liquefied sites in the
Kanto region. Because of their geomorphologic
condition, the following sites liquefied:
a) Artificially reclaimed lands along Tokyo Bay and
the Pacific Ocean
b) Filled lands on former ponds and marshes
c) Sites excavated to get iron sands or gravels and
then refilled.
In addition, embankments and foundations of river
dikes and refilled soils for sewage pipes liquefied.
Liquefaction occurred along the Pacific coast of
the Tohoku region, but the liquefied sites were obscured by a huge tsunami that hit the coastal area
Gum
ma
4. EFFECT OF LIQUEFACTION ON
STRUCTURES IN URAYASU CITY
(1) Liquefied area in Tokyo Bay area
Fig.3 is a map of the liquefied zones in the Tokyo
Bay area5). The whole area of the northern part of
Tokyo Bay liquefied, but in the eastern and western
parts of Tokyo Bay, liquefaction was observed only
in spots. In the northern part of Tokyo Bay, the
ground surface was covered with boiled sands all
around the reclaimed lands in Shinkiba in Tokyo,
Urayasu City, Ichikawa City, Narashino City and
western Chiba City. In contrast, boiled sands were
observed only here and there in the reclaimed lands
in Odaiba, Shinonome, Tatsumi, Toyosu and Seishin
in Tokyo and in eastern Chiba City. The total liquefied area from Odaiba to Chiba City reached about 41
km2. Many houses, roads, and lifeline facilities were
severely damaged in the liquefied zones. The most
serious damage was in Urayasu City, where about
85% of the city liquefied.
The epicentral distance of the liquefied area in
Tokyo Bay is very long, around 400 km. However,
the distance from the boundary of the rupture plane is
Tochigi
Ibaraki
Kanto Region
Saitama
Seishin
Tatsumi
Funabashi
Takahama
Urayasu
D’
Tokyo
Kana
gawa
Chiba
Shinkiba
Odaiba Shinonome
Liquefied
site
Takasu
D
Liquefied zone
2km
20
0
20(km)
4
Fig.3 Liquefied areas from Odaiba in Tokyo to Chiba5).
Fig.2 Sites of soil liquefaction in the
Kanto Region caused by the
Great East Japan Earthquake
of 20115).
only 110 km because the rupture plane is very wide.
(3) Zones of structural damage
Fig.7 shows the areas of Urayasu City where liquefaction damaged sewage facilities, roads and
D
D’
Altitude(m)
Altitude(m)
Fig.4 History, location and extent of land reclamation in
Urayasu6).
B
F
As
Ac
‐25
As
As
‐25
Na
‐50
‐50
Ds
‐75
‐75
1km
Fig.5 Detailed soil cross-section of Urayasu City (Slightly
modified from the report by Urayasu City6)).
350
平均値μ=43.8
標準偏差σ=30.4
サンプル数N=410
Average FC=43.8%
300
Numberデータ数
of samples
(2) History of reclamation and soil in Urayasu
City
The reclamation of coastal areas in Tokyo Bay
started in the seventeenth century and accelerated
with an increase in population. The history of reclamation work in Urayasu City is summarized in
Fig.46). Urayasu City is divided into three towns,
Motomachi, Nakamachi and Shinmachi, which mean
old, middle and new towns, respectively. The ground
of Motomachi formed naturally at an estuary of Edo
River. On the other hand, zones A, B and C in
Nakamachi were reclaimed from 1965 and zones D,
E and F in Shinmachi were reclaimed from 1972. The
area of each zone is 1.0 to 3.5 km2, and the total area
of Nakamachi and Shinmachi is 14.36 km2, which is
about 85% of the area of Urayasu City.
Four months after the earthquake, a technical
committee chaired by Prof. K. Ishihara was organized by the Urayasu City Government to study the
mechanism of liquefaction-induced damage and
restoration works. The committee conducted detailed
soil investigations, laboratory tests and analyses, and
reported valuable results6). The following is a brief
summary of the report.
Fig.5 shows a soil cross-section along the line
Urayasu D-D’ in Figs.3 and 4 through Motomachi,
Nakamachi and Shinmachi. In the reclaimed zone, a
filled layer of mainly hill sand (B) and a filled layer
of dredged sandy soil (F) with low SPT N-values
averaging 5.46 are deposited with a thickness of
several meters. Though layer F had to be liquefied,
the fines content of layer F is very large, with an
average value of about 44%, and very scattered from
FC=0% to 100%, as shown in Fig.6. An alluvial sand
layer (AS) with an average SPT N-value of 12.9 underlies the filled layer. The average fines content of
layer AS is 30.9%. A very soft alluvial clay layer (Ac)
is deposited under the AS layer with a thickness of 10
to 40 m, increasing in thickness as it approaches the
sea. A diluvial (Pleistocene) dense sandy layer (Ds)
with an SPT N-value of more than 50 underlies the
alluvial clay layer. The water table is shallow, averaging 1 to 2.5 m below ground level (G.L.).
Urayasu City contains light structures, such as
wooden houses, and heavy structures, such as
high-rise buildings and elevated bridges. These
heavy structures are supported by long piles which
mainly penetrate to the depth of the diluvial dense
layer.
250
200
μ‐σ
μ+σ
μ
150
100
50
0
0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100
FC (%) F (%)
Fines content,
C
Fig.6 Frequency distributions of fines content FC for dredged
soils6).
houses. Liquefaction occurred only in Nakamachi
and Shinmachi, as Motomachi is built on natural
land. In Motomachi an alluvial sand (AS) layer is
deposited just under the water table, as shown in
Fig.5. If the AS layer had liquefied, sand boils should
have appeared. However, no sand boils, nor damage
to houses and lifeline facilities, occurred. Therefore,
it can be estimated that the AS layer basically was not
liquefied by the 2011 Great East Japan Earthquake,
though some loose parts of the layer might have
当代島三丁目
液状化及び下水道施設
破損エリア
西
鉄東
団地下
線
当代島二丁目
営
北栄二丁目
当代島一丁目
西線
下鉄東
営団地
Zones where
severe damage
to houses
occurred
北栄一丁目
道路の被害大エリア
北栄三丁目
営団地下鉄東西線
猫実五丁目
猫実四丁目
北栄四丁目
猫実三丁目
道路の被害中エリア
堀江四丁目
海楽二丁目
猫実二丁目
堀江三丁目
道路の被害小エリア
堀江二丁目
猫実一丁目
美浜四丁目
海楽一丁目
堀江一丁目
堀江五丁目
堀江六丁目
美浜五丁目
入船五丁目
富士見二丁目
美浜三丁目
美浜一丁目
入船六丁目
東野一丁目
富士見一丁目
入船四丁目
日の出二丁目
美浜二丁目
富岡一丁目
東野二丁目
入船一丁目
富士見三丁目
日の出一丁目
富士見四丁目
入船二丁目
入船三丁目
富岡二丁目
日の出三丁目
京葉
ＪＲ
線
富岡四丁目
東野三丁目
日の出四丁目
明海一丁目
日の出六丁目
今川一丁目
富岡三丁目
富士見五丁目
日の出五丁目
弁天一丁目
今川二丁目
舞浜二丁目
明海二丁目
明海四丁目
今川四丁目
弁天二丁目
日の出七丁目
高洲一丁目
今川三丁目
明海三丁目
弁天四丁目
日の出八丁目
明海五丁目
ＪＲ
京
葉線
高洲二丁目
高洲五丁目
明海六丁目
弁天三丁目
鉄鋼通り一丁目
高洲四丁目
明海七丁目
舞浜三丁目
ＪＲ
京
高洲三丁目
葉線
高洲六丁目
鉄鋼通り二丁目
デ
ィ
ズ
ニ
ー
リ
ゾ
ー
ト
ラ
イ
ン
高洲七丁目
鉄鋼通り三丁目
高洲九丁目
高洲八丁目
港
舞浜
千鳥
Areas surrounded
応急危険度調査対象
by lines
Black: Liquefied and sewage facilities
were 特に建物被害の多い所
damaged
Red: Roads were
severely damaged
護岸の被害が大きい所
Blue: Roads were damaged
Yellow: Roads were slightly damaged
1km
Acceleration (Gal)
200
CHB008EW(14:46) EW
100
0
-100
Velocity (Kine)
-200
0
50
100
150
Time (sec)
200
250
300
200
CHB008EW(15:15) EW
100
0
-100
-200
0
50
100
150
Time (sec)
200
250
300
40
40
CHB008EW(14:46) EW
20
0
-20
-40
0
50
100
150
Time (sec)
200
250
300
(1) Main shock (May 11,14:46)
Velocity (Kine)
Acceleration (Gal)
Fig.7 Zones of Urayasu City where roads, sewage pipes and houses were severely damaged6).
CHB008EW(15:15) EW
20
0
-20
-40
0
50
100
150
Time (sec)
200
250
300
(2) Afteshock (May 11, 15:15)
Fig.8 Acceleration and velocity waves measured by Urayasu K-NET during the main shock and the biggest aftershock7).
liquefied and some parts of the dredged sandy soil
under the water table might have liquefied in
Nakamachi and Shinmachi.
Sewage pipes, manholes, roads and houses were
damaged in the liquefied areas, but the severity of
damage to roads and houses varied from place to
place.
(4) Accelerations during main shock and aftershock
The duration of shaking in the 2011 Great East
Japan Earthquake was extremely long, and the main
shock was soon followed by a big aftershock. Surface
acceleration during the main shock was not high,
around 160 Gal. Fig.8 shows the accelerographs and
velocities recorded during the main shock and the
aftershock by K-NET7) in Urayasu on ground where
liquefaction did not occur.
Some inhabitants of Urayasu City observed the
boiling of muddy water immediately after the main
shock, while others saw spouts of muddy water five
to nine minutes after the main shock8). Surprisingly,
some inhabitants testified that boiling did not occur
during the main shock but occurred during the aftershock. Some excess pore-water pressure may have
built up during the main shock, causing complete
liquefaction during the aftershock. It is impossible to
evaluate the liquefaction time, but it must have differed by place because of the long duration of the
main shock and the subsequent large aftershock.
Shaking continued for a long time after the occurrence of liquefaction.
(5) Damage to flat roads
As described in Table 2, there are four grades of
planar roads in Urayasu City: national roads, pre-
fectural roads, main city roads and normal city roads.
The total length of damaged roads amounted to about
80 km. These roads were designed without considering liquefaction because no seismic design codes
which consider liquefaction have been developed for
flat roads. Liquefaction caused several phenomena to
interrupt traffic:
i) much muddy water boiled onto roads (see Fig.9);
ii) road asphalt heaved, was thrusted or was deformed
into waves at many sites (see Fig.10);
iii) many small road cave-ins occurred several
months after the earthquake.
(6) Damage to river and sea walls
Three sides of Urayasu City face Tokyo Bay and
Table 2 Extent of road damage in Urayasu City6).
Length Damage Damage (km)
length (km) rate (%)
National road
Prefectural road
City main road
City normal road
4.5
‐
‐
7
1.9
27
28
12
43
195
66
34
Fig.9 Cars stuck in boiled muddy water in Urayasu
City6).
Fig.10 Thrusted road pavement in Urayasu City6).
are protected by sea walls. Two rivers, the Sakai
River and the Miake River, transverse Urayasu City
from northwest to southeast and are protected by
river walls. These sea and river walls were not designed to withstand liquefaction damage because
reclamation work for the walls started only a few
years after the 1964 Niigata Earthquake, when liquefaction was first recognized. Though many sea and
river walls are found in the liquefied area, only a few
walls were damaged, as shown in Fig.4. These sea
and river walls slightly expanded and settled. Fig.11
shows the damaged concrete river wall at Sakai river
in Urayasu City, and Fig.12 shows a cross-section of
this wall.
During the 1995 Hyogoken-nambu Earthquake,
many caisson quay walls and sea walls moved and
tilted toward the sea in the liquefied area, resulting in
large lateral flows of the ground behind the walls.
The failure of the quay wall is a complex dynamic
phenomenon. To explain from the point of view of
the design, the failure process can be summarized as
follows: i) a strong inertial force due to very high
acceleration, ii) a decrease in shear strength due to an
increase in excess pore-water pressure in the replaced
sand beneath the caisson walls, and iii) an increase in
earth pressure due to a rise in excess pore-water
pressure in the ground behind the wall. In contrast,
only a few sea and river walls moved and tilted in
Urayasu and other cities along Tokyo Bay during the
2011 Great East Japan Earthquake. The reasons for
the difference in damage to these walls caused by the
two earthquakes are uncertain, but they may be the
different wall types and strengths, different soil
conditions, different slopes of the ground behind the
walls, the depth of liquefied soil and different accelerations.
(7) Damage to lifeline structures
Lifeline facilities for water, sewage, gas, electric
power and telegraphs were severely damaged in the
liquefied area. Though seismic design codes for these
Fig.11 Moved and settled wall along Sakai River in
Urayasu City6).
A.P　m
5.0
Table 3 Extent of damage to public waste water pipes and
manholes in Urayasu City6).
Concrete
4.0
3.0
2.0
Motomachi Nakamachi Shinmachi
Blast furnace slag
H.W.L　A.P+2.0m
Pipe
Length (km)
1.0
0.0
94.4
33.6
0
19.2
4.6
Damage rate (%)
Wood Pile
-1.0
-2.0
84.2
Damaged length (km)
Manhole
Blast furnace slag
Concrete sheet pile
Fig.12 Cross-section of the moved and settled wall
along Sakai River in Urayasu City6).
0
20
14
2,348
2,799
1,069
Damaged number
0
328
147
Damaged rate (%)
0
12
14
Number
Kairaku
Horie Nekozane
Mihama
Fujimi
Higashino
Irifune
Tomioka
Imagawa
Maihama
Tokyo
Disneyland
Hinode
Akemi
Benten
Tekkodori
Takasu
Minato
管路被害（要補修箇所）
Damaged pipe
Damaged
pipe
Chidori
マンホール浮上
Uplift of manhole
Uplift
of manhole
マンホール沈下
Settle of manhole
Settling
of manhole
マンホール破損・ズレ
Shear of manhole
Shearing
of manhole
マンホール蓋のみ
Damage to lid of Damage
to lid of
manhole
manhole
Fig.13 Sites of damaged waste water pipes and manholes in Urayasu City6).
facilities started to consider the effect of liquefaction
from about 1980, as shown in Table 1, many lifeline
facilities in Urayasu City were constructed before
that date. So, many facilities were damaged due to
liquefaction. Detailed assessments of damage to
buried pipes are not available because not all damaged pipes have been excavated and permanently
restored.
Leakage occurred at 608 sites along water pipes,
and water service for 33,000 households was
stopped. Water pipes were broken at 122 of the
leakage sites, and joints were pulled out or sheared at
366 sites.
Sewage pipes and manholes for waste water and
rain water were severely damaged in a wide area.
Urayasu City was served by 20.7 km of main sewage
pipes and 191.5 km of branch sewage pipes. Of these
pipes in Nakamachi and Shinmachi, 20% and 14%,
respectively, were damaged, whereas no pipes were
damaged in Motomachi, as summarized in Table 3.
Fig.13 shows the sites of damaged waste water pipes
and manholes. Sewage pipes were deformed,
cracked, broken and meandered, and joints were
sheared or disconnected, as shown in Fig.14 (1).
Muddy water seeped into the damaged pipes for
127.2 km and closed pipes completely for about 60
km.
Many sewage manholes were cracked and sheared
in a horizontal direction and filled with muddy water,
as shown in Fig.14 (2), while a few manholes were
lifted or slightly settled, as shown in Fig.14 (3).
Muddy water filled almost all manholes in
Nakamachi and Shinmachi. It took 34 days to restore
these damaged pipes and manholes provisionally.
Shear damage to manholes had not occurred during past earthquakes in Japan. Many sewage manholes were lifted but not sheared during the 1993
Kushiro-oki earthquake, the 2003 Tokachi-oki
earthquake and the 2004 Niigataken-chuetsu earthquake9). During the construction of the manholes and
(1) Meandered pipe with disconnected joints
(2) Sheared
(3) Uplifted
manhole
Fig.14 Schematic diagram of damage to sewage pipes and
6)
manholes in Urayasu City .
Fig.15 Uplifted water tank for emergency use in Urayasu
City6).
pipes, the ground was excavated to a width of about 2
m. After placing the manholes and pipes, the excavated area was filled with sand. During past earthquakes, only the fill soils were liquefied, but during
the 2011 Great East Japan Earthquake, both the fill
soils and the surrounding soils were liquefied in
Urayasu. Therefore, the horizontal displacement of
the liquefied soil around the pipes in Urayasu caused
by the 2011 earthquake must have been larger than
the horizontal displacement caused by previous
earthquakes. Moreover, as the main shock of the
2011 earthquake was very long and was followed by
a big aftershock, shaking must have continued for a
long time after the occurrence of liquefaction. The
large horizontal displacement of liquefied ground
had to have caused the disconnection of the pipe
joints and the shear failure of the manholes, allowing
the influx of muddy water into the pipes and manholes.
In gas facilities, gas holders, governor stations and
high-pressure pipes were not damaged and middle-pressure pipes were only slightly damaged. On
the other hand, some low-pressure gas pipes were
broken and muddy water filled the pipes to a length
of 11 km, resulting in the shut-down of gas service
for 8,631 homes.
Buried cables for electric power distribution were
damaged at six sites. Manholes for telegraph lines
were sheared similar to the sewage manholes.
Moreover, electric and telegraph poles seriously
settled and tilted here and there.
A steel water tank for emergency use buried to a
depth of G.L.-2.4 m was lifted, as shown in Fig.15,
though the tank did not break. The tank is 3.0 m in
diameter, 15.1 m in length, 100 m3 in capacity and
fixed with belts to prevent uplift; the belts must have
failed.
(8) Damage to houses
According to the Ministry of Land, Infrastructure,
Transport and Tourism (MLIT), about 27,000
wooden houses in Japan were damaged due to liquefaction caused by the 2011 Great East Japan
Earthquake. Strip footing foundations or mat foundations are used for houses in Japan. In the design of
wooden houses, liquefaction has not been considered, whereas the design code for other buildings has
considered liquefaction since 1974, as shown in Table 1. This is the main reason such a large number of
houses were damaged. In contrast, some houses
supported by steel piles or cement-mixed soil piles
penetrating to the depth of the non-liquefied layer did
not settle.
In Urayasu City, severely damaged houses were located in the zones shown in Fig.7. Many houses settled
and tilted, though they suffered no damage to walls and
Fig.16 Settled and tilted houses in Urayasu City.
Table 4 Number of damaged houses in Urayasu City under
old and new standards (Counted on Sept. 3, 2011).
Grade of damage
Number of houses
Old standard
New standard
Totally collapsed
8
10
Large-scale half
collapsed
0
1,509
33
2,102
Partially damaged
7,930
4,848
No damage
1,028
963
Total
8,999
9,432
half collapsed
each other, they tilt toward each other, and if four
houses are close together, they tilt toward their center
point8), 11) as shown in Fig.16.
Even in liquefied areas, several zones did not liquefy or suffer damage to houses because the ground
in these zones had been improved. One example is a
housing lot in Irifune where sand compaction piles
(SCPs) were installed in the foundations of mainly
three-story houses to increase the bearing capacity
and to prevent liquefaction, and gravel drains (GDs)
were installed in the foundations of mainly two-story
houses to mitigate liquefaction8). Each type of
building had a spread foundation (continuous foundation) supported by nodular piles 8 m long. Following the earthquake, sand boils were observed in
unimproved areas around the housing lot. However,
no sand boils were seen within the improved area and
no damage occurred to buildings constructed on
ground improved by either the SCP method or the
GD method.
windows, as shown in Fig.16. In the greatly tilted
houses, inhabitants felt giddy, sick and nauseated, and
found it difficult to live in their houses after the earthquake. In May 2011, the Japanese Cabinet announced a
new standard for the evaluation of damage to houses
based on two factors, settlement and inclination. A new
class of “large-scale half collapsed house” was also
introduced, and houses tilted at angles of more than
1/20, of 1/20 to 1/60, and of 1/60 to 1/100 were judged
to be totally collapsed, large-scale half collapsed and
half collapsed houses, respectively, under the new
standard. The number of damaged houses in Urayasu
City by the new standard in listed in Table 4. The
number of totally collapsed, large-scale half collapsed,
half collapsed partially damaged and undamaged
houses in Urayasu City was 10, 1,509, 2,102, 4,848 and
963, respectively, as of Sept. 3, 2011. According to a
previous study on the non-uniform settlement of houses10), several factors affect such settlement. Among
them, the effect of adjacent houses was dominant in the
Abehikona housing lot during the 2000 Tottoriken-seibu Earthquake10). A similar tendency was observed in the Tokyo Bay area. If two houses are close to
(9) Damage to heavy structures supported by
piles
Many road and railway bridges supported by piles
were not damaged, though liquefaction occurred
around the piles. Fig.17 shows an elevated bridge on
the Keiyo Railway Line which is supported by prestressed concrete (PC) and steel and concrete composite (SC) piles, as illustrated in Fig.18. In the
design of the pile foundation, liquefaction was assumed to be probable and the lateral bearing capacity
of the liquefiable layer, from the water level to G.L.
-10 m, was assumed to be zero12). Thus, SC piles,
which are stronger than PC piles, were installed to a
depth of -10 m.
There are many buildings supported by piles in the
liquefied area. These buildings were not damaged,
but the inhabitants of some apartment buildings were
forced to live in inconvenient conditions for weeks
because of the shutdown of lifeline facilities and
because of ground settlement at the entrances of their
apartment houses. At the fire station shown in Fig.19,
ladder trucks could not enter the fire station due to the
settlement of the road in front of the station.
During the 1995 Hyogoken-nambu Earthquake,
many piles for road bridges and apartment buildings
were damaged due to liquefaction in Kobe City. In
contrast, no damage occurred to road bridges and
apartment buildings with similar pile foundations in
Urayasu and other cities in the Tokyo Bay area. This
difference in damage may be due to the larger amplitude of shaking in Kobe, where the recorded accelerations were about three times the accelerations
recorded in the Tokyo Bay area.
5. LIQUEFACTION-INDUCED DAMAGE
TO SEVERAL STRUCTURES IN
TOHOKU AND KANTO REGIONS
(1) Damage to river dikes
River dikes settled and slid seriously at many sites
in the Tohoku and Kanto regions. According to the
Keiyo Railway
Line
Fig.17 Undamaged elevated bridge on the Keiyo
Railway Line at Shin-Urayasu Station.
Tohoku and Kanto Regional Development Bureaus
of the MLIT, there were 1,195 sites of dike damage in
the Tohoku region and 939 sites in the Kanto region.
Most river dikes in these regions were designed and
constructed without considering liquefaction. In the
Tohoku region, a few dikes which had been damaged
during earthquakes in 1978 and 2003 and restored to
prevent liquefaction-induced damage suffered no
damage from the 2011 Great East Japan Earthquake.
After this earthquake, technical committees were
organized by the two regional development bureaus
to ascertain the mechanism of failure and select appropriate restoration methods.
In the Kanto region, dikes along the Tone, Kokai,
Kinu, Hinuma, Naka and other rivers were damaged,
as shown in Fig.2013). The types of damage included
settlement, as shown in Fig.21, slides, longitudinal
cracks and transverse cracks. Serious damage occurred at 55 sites. The mechanism of the damage at
the seriously damaged sites was studied based on soil
investigation. It was concluded that 51 sites suffered
damage triggered by liquefaction. As shown in
19.8m
N
SPT N
0 50
10
20
Tochigi
Upper pile
Kinu River
Gunma
Watarase River
Tone River
Kuji River
Naka River
Ibaraki
Lower pile
Kokai River
Saitama
Ara River
Lake Kasumigaura
Tone River
30
40
50
Tama River
Piles (φ=600mm)
Upper pile : SC pile
Lower pile : PC pile
60
Mt.Fuji
Tokyo
Chiba
Kanagawa
: Damage zone
0
30
60km
Fig.20 Sites of river dike damage in the Kanto region
(modified from MLIT13)).
Fig.18 Diagram of pile foundation of Keiyo Railway
Line12).
Fig.19 Road subsidence in front of a fire station.
Fig.21 Settled river dike along the right bank of Tone
River.
Fig.22, there were three patterns of liquefied soil: 1)
the foundation ground liquefied, 2) the lower part of
the embankment liquefied, and 3) both foundation
ground and embankment liquefied. In the latter two
types, the water tables inside the embankments were
higher than the water tables in the surroundingground. In the restoration work, several appropriate
methods were selected in accordance with the type
and severity of damage to prevent damage during
future earthquakes, as shown in Fig.23.
(2) Damage to sewage pipes and manholes
According to the MLIT, sewage pipes and manholes were damaged in 132 cities, towns and villages.
Of 65,001 km of sewage pipes in the cities, towns and
villages, 642 km were damaged14). As shown in
Fig.24, 65.9% of the damage to pipes was due to the
liquefaction of filled soils and 24.5% was due to the
liquefaction of both filled soils and the surrounding
ground. Of the damage to manholes, 41.7% was due
to the liquefaction of filled soils and 26.7% was due
to the liquefaction of filled soils and the surrounding
ground. The damage due to the liquefaction of both
filled soils and surrounding ground mainly occurred
along Tokyo Bay, as shown in Fig.25, because liquefaction occurred in a wide area of reclaimed land,
as mentioned before.
Most of the damaged pipes and manholes were
constructed without consideration of liquefaction. A
few pipes and manholes that had been restored with
Embankment
Embankment
Seismic force
Liquefaction
Liquefaction
Liquefaction of filled soil
Sand
Clay
Clay
(1) Liquefaction of ground
(2) Liquefaction of embankment
Embankment
Embankment
Liquefaction of surrounding
ground and filled soil
Tsunami
Slide or settlement of fill in
housing lots
Others
Liquefaction
Clay
Liquefaction
Liquefaction
Sand
(3) Liquefaction of ground and embankment
Sand
Clay
(4) Liquefaction of ground and embankment
Fig.24 Causes of damage to sewage pipes in the 132
damaged cities, towns and villages14).
Fig.22 Patterns of soil liquefaction along river dikes13).
Liquefied part
Restoration method
Schematic diagram
Uplift of sewage pipes and
manholes due to the
liquefaction of filled soils
River level
<Before earthquake>
Liquefied layer
Ground water level
Non-liquefied layer
Remarkable damage to
sewage pipes and manholes
due to the liquefaction of
surrounding grounds and
filled soils
Drainage
Lower part of
embankment
Drain + Waste channel
Densification
by sand compaction
pile
Deep mixing
S.C.P + Waste channel
Fig.25 Areas where two patterns of damage to sewage
pipes and manholes dominated14).
Deep mixing method
River level
<Before earthquake>
Ground water level
Liquefied layer
Non-liquefied layer
Foundation
ground
Sheet pile
Sheet pile +
Drain + Waste channel
Deep mixing
Deep mixing method
Embankment
+
ground
Drainage
+
Sheet pile
Sheet pile +
Drain + Waste channel
Fig.23 Diagram of methods to restore damaged river dikes
in the Kanto region (modified from MLIT13)).
Non liquefiable
Non liquefiable
(1) Dissipation of excess
pore water pressure
(2) Balance by counter weight
Fig.26 Diagrams of successful measures for preventing
the uplift of existing manholes14).
countermeasures after the 2008 Iwate-MiyagiNairiku Earthquake were not lifted during the 2011
Great East Japan Earthquake. These pipes and
manholes had been restored by one of two measures
proposed by the Technical Committee on the Sewer
Earthquake Countermeasures in 2005: i) fill ditches
with gravel instead of sand, and ii) mix the filled sand
with cement.
Two other recently developed methods to prevent
the uplift of existing manholes, illustrated in Fig.26,
had been applied in some parts of the liquefied areas
and successfully served their purpose.
(3) Damage to plants
There are many electric power plants, oil tank
yards, factories and warehouses in the liquefied areas
along the coasts of Tokyo Bay and the Pacific Ocean.
Fig.27 shows a tilted oil tank yard fence15). The extent of damage to plants is still unknown because
most of the plants belong to private companies and
site surveys are difficult to undertake. However,
serious damage, such as the burning of oil tanks, did
not occur in the liquefied areas. Most likely, the main
reason for this lack of serious damage is that the
important facilities, such as oil tanks and electric
power plants, were designed based on seismic design
codes that considered liquefaction and required the
use of appropriate pile foundations or soil improvement. Many old oil tanks constructed before
liquefaction was considered in seismic design codes
had been strengthened against liquefaction by special
measures, such as surrounding the tanks with sheet
piles to prevent liquefaction-induced settlement.
coast, it is not easy to judge whether damage occurred due to liquefaction or not because a huge
tsunami washed away all traces of liquefaction.
Sugano reports that obvious liquefaction-induced
damage occurred at two ports, Souma Port and
Onahama Port, where the corners of quay walls
moved toward the sea16). At Onahama Port, an apron
behind a quay wall settled below the rails for cargo
loaders.
At Sendai Airport, an underpass road and an underground conduit had been constructed beneath the
tarmac at four points. For their construction, the
ground had been excavated. After their construction,
the excavated area was filled with sand. Subsequently, special techniques to prevent liquefaction,
i.e., compaction grouting, and high-pressure injection, were applied to the sand fill at three of these
points. No liquefaction accompanying the Great East
Japan Earthquake occurred at these three points.
However, at the fourth point, which had not been
improved, the tarmac settled17).
(5) Damage to a tailings dam
Three abandoned tailings dams failed in the
Tohoku and Kanto regions. The Kayakari tailings
dam built by Ohya Mining, located near Kesen-numa
City in Miyagi Prefecture, failed due to the liquefaction of gold slime, as shown in Fig.28. A
cross-section of the failed slope is shown in Fig.2918).
Slime from the failed slope flowed down a small river
and destroyed a house.
(4) Damage to port and harbor structures
There are many ports and harbors along the coasts
of the Pacific Ocean and Tokyo Bay. No serious
damage was inflicted on ports and harbors in the
liquefied areas along Tokyo Bay. Along the Pacific
Fig.28 Liquefied and failed slope of Kayakari tailings
dam.
Before failure
40
(m)
After failure
Slime
20
Rock
0
Fig.27 Tilted oil tank yard fence along the Pacific
Ocean coast15).
0
25
50 (m)
Fig.29 Cross-section of failed slope at Kayakari tailings
dam18).
The Kayakari tailings dam was constructed by the
inner filling method and finished in 1966. After the
Mochikoshi tailings dam failed due to liquefaction
during the 1978 Izuohshima-kinkai Earthquake,
liquefaction consideration was introduced in the
design code for tailings dams in 1980. Then, the
probability of liquefaction-induced damage at many
tailings dams was estimated by conducting soil investigations and tests. The Kayakari tailings dam was
one of those examined, and the examiners concluded
that there was little or no probability of such damage.
However, the seismic intensity that hit the Kayakari
tailings dam during the Great East Japan Earthquake
was fairly higher than the examined intensity.
2)
3)
4)
5)
6)
6. CONCLUSIONS
Liquefaction-induced damage to structures during
the 2011 Great East Japan Earthquake has been described based on site investigations conducted by the
authors and others, and the following conclusions are
derived:
1) Because of their geomorphologic condition, artificially reclaimed lands along Tokyo Bay and the
Pacific Ocean, filled lands on former ponds and
marshes, and sites of excavation to get iron sands or
gravels that had been refilled, liquefied.
2) In Urayasu City, where about 85% of the city area
liquefied, wooden houses, flat roads and buried pipes
were seriously damaged due to liquefaction, whereas
buildings and bridges supported by piles were not
damaged even though the ground surrounding them
liquefied.
3) River dikes were damaged at about 2,100 sites,
mainly because of the liquefaction of the foundation
ground and/or embankments.
4) Sewage pipes and manholes sustained two types of
damage: i) lifting due to the liquefaction of fill soils,
and ii) the shear failure of manholes and pull-out of
pipe joints due to the liquefaction of fill soils and the
surrounding ground.
ACKNOWLEDGMENT: Some of the results cited
in this paper are quoted from reports by Technical
Committees organized by the Ministry of Land, Infrastructure, Transport and Tourism, Ministry of
Economy, Trade and Industry, and Urayasu City
Government. The authors would like to express their
sincere appreciation to them.
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
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