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

RELATIONSHIP BETWEEN AGE OF GROUND AND
LIQUEFACTION OCCURRENCE IN THE 2011 GREATEAST JAPAN EARTHQUAKE
Masanori ISHIHARA1 and Tetsuya SASAKI2
1Senior Researcher, Soil mechanics and Dynamics Research Team, Geology and GeotechnicalEngineering Research Group, Public Works Research Institute
Tsukuba, Japan, isihara@pwri.go.jp
2Team Leader, ditto,Tsukuba, Japan, t-sasaki@pwri.go.jp

ABSTRACT: Significant damage was caused in the northern part of the Tokyo Bay bysoil liquefaction in 2011 Great East Japan Earthquake. The areas where boiled sands
due to liquefaction were observed extensively were distributed mainly in recently
reclaimed land. Therefore, this research gathered amount of data on boring conducted in
Kanto region and relationships between occurring of liquefaction and SPT N-values
were organized. As the result some differences between recently reclaimed land and,reclaimed land in old time or natural bed ground were confirmed.
Key Words: liquefaction, reclaimed land, age of ground, Great East Japan earthquakeINTRODUCTION
Sand boils and water gushing due to liquefaction occurred in extended areas of reclamation grounds inthe northern part of the Tokyo Bay and the downstream section of the Tone River in the Great East
Japan earthquake. Especially in the northern part of the Tokyo Bay amount of boiled sand andgushing water interfered with the lives of residents and many private houses, sewage
manholes, pipes and etc. were damaged due to liquefaction (JGS 2011, etc).
The damage was mainly caused on the east side of the northern part of the Tokyo Bay,
Chiba prefecture. Areas where liquefaction occurred in the earthquake are limited to mainlyreclaimed land.
In other hand, areas where liquefaction occurred in the west side of the northern part of
the Tokyo Bay, Tokyo Metropolitan, were quite smaller than the east side, although
reclamation works have been conducted after the 16th century in the west side. These areas
were limited the reclaimed land beside the coast.
A point in common between the reclaimed land where liquefaction was observed in theeast and in the west was recently reclaimed land after the Showa era (after 1926). Therefore,
it is pointed out that young grounds are likely to have a smaller resistance againstliquefaction and, old grounds and natural grounds are likely to have a stronger resistance.
Koseki and Ohta (2001) reported that liquefaction resistance is influenced by the aging of771

the sample based on element tests. But, the mechanism of improvement of liquefaction
resistance due to aging has not been clarified sufficiently.
In this research amount of data on boring conducted in Kanto region was collected, andrelationships between occurring of liquefaction in the earthquake and SPT N-values were organized. In
addition, a map showing distribution of thickness of liquefiable sandy soil created in order to beapplied to future investigation will be introduced.

COLLECTION OF DATA ON BORING
A total of 173 pieces of data on boring was gathered from the locations shown in Fig. 1. These data
were collected based on the following perspectives.
a) In the Kanto Region, locations with liquefaction in the northern part of the Tokyo Bay where theoccurrence of liquefaction was significant and nearby areas without liquefactionb) Among river levees damaged chiefly by liquefaction, such as the downstream section of theTone River and along the Kokai River and the Naka River, locations where a boring
investigation was conducted after the earthquakec) Other locations around the Kanto Region
The existence of liquefaction was determined based on the investigations by the Kanto Regional
Development Bureau and the Japanese Geotechnical Society. Furthermore, the investigations werebased on the traces of sand boils and water gushing.
In addition, the following conditions were applied when selecting data on boring from the abovesites.
d) A sand layer which will be the target of a liquefaction evaluation is present.
e) The data must represent its area, meaning that multiple pieces of data on boring with similar soil
layer configurations from nearby areas should not be selected.
f) The depth of boring is sufficient, and the groundwater level is recorded. Even when the selectedboring does not clarify that the liquefaction layer is not located at a deeper location than thedepth of boring, the data is accepted if the investigations on boring conducted in nearby areas
confirm such a condition. The same rule applies to the groundwater; the data is accepted if thegroundwater level can be estimated based on boring investigations conducted in nearby areas.
g) The period of reclamation is roughly known (Endoh 2004, etc.).
The data on boring is provided by the Ministry of Land, Infrastructure, Transport and Tourism(MLIT) Kanto Regional Development Bureau as well as the Civil Engineering Center of the Tokyo
Metropolitan Government, Water quality Division of the Chiba Prefectural Government (Informationbank), and Public Works Department of the Chiba Prefectural Government. Some of them areorganized into a database and made available to the public.
Table 1 shows the number of boring sites at each period of reclamation. One fourth of the sites
were located in the area where liquefaction was observed. The numbers does not make much sense
because the data on boring is collected as described above.
Table 1 The number of boring sites at each era

Natural groundOld reclaimed land until 1925 (Edo,Meiji, Taisyo era)
Recent reclaimed land after 1926
(Showa era)
Total

Number of boring sites
With liquefaction
Without liquefaction
95261
29

32683

3449

173

46

127772

040kmWith
Withoutliquefaction liquefaction

Natural groundOld reclaimed land until 1925
Recent reclaimed land after 1926
051015Fig. 1 Locations of the collected data on boring

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20[km]
40

RELATIONSHIP BETWEEN SHEAR STRESS RATIO AND CONVERTED N VALUE
A relationship between maximum shear stress ration during the earthquake and N-value converted tocorrespond to effective overburden pressure of 98 kN/m2 was organized. The maximum shear stressration, L was obtained by the following equation from Specifications for Highway Bridges (2002).

L   d k hg  v  v '(1)where,  d is reduction coefficient in the depth direction of the shear stress ratio and k hg ishorizontal seismic coefficient at the ground surface.
The maximum acceleration distribution (Kataoka 2011) produced based on strong motion
observation records of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the Japan
Meteorological Agency, and the National Research Institute for Earth Science and Disaster Prevention
normalized by the gravitational acceleration was used as the horizontal seismic coefficient.
Set of L and N1 is obtained at each depth from one boring site. The existence of liquefaction isevaluated based on the existence of trace of sand boils or water gushing; thus, liquefaction is likely tohave occurred at a relatively shallow sand layer. In addition, if liquefaction is contained within alimited thin layer, the event is not likely to result in sand boil or water gushing. Therefore, the second
smallest N1 and L at the depth where N1 was the second smallest up to a depth of 10m was extract froma boring site.
The relationship between maximum shear stress ration and converted N-value was shown in Fig.
2. Black curved lines in these graphs are the relationship between cyclic triaxial strength ratio, same asliquefaction resistance, and converted N-value at fine contents of 0 % to 10% that was stipulated inSpecifications of Highway Bridges. A point above the curved line was labeled as having liquefaction
in liquefaction assessment. Therefore, it is to be desired that the curved line locates at the borderNatural Old

New

With Liquefaction
1.2

1.2

1.2

All

Shear stress ratio during the earthquake, L

Natural Old New
Without Liquefaction

1.0

NaturalNatural + Old
1.0

1.0

0.8

0.8

0.8

0.6

0.60.6

0.4

0.4

0.4

0.2

0.2

0.2

Specifications for
Highway Bridges

0.0

0.0
0102030400.00102030

400102030

40

2N-value converted to correspond to effective overburden pressure of 98 kN/m , N1Fig. 2 Relationship between the shear stress ratio during the earthquake at each fine-grained fraction
and converted N values Locations of the collected data on boring.

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between the points with liquefaction and without liquefaction (Seed 1971). But, if the line envelopes
the points with liquefaction at least, the relationship could evaluate liquefaction resistance in safetyside.
All points were plotted in the left graph. Some points with liquefaction located above the curved
line in the range between shear stress ratio of 0.2 and 0.3. Points except recently reclaimed land wereplotted in the center graph. In the center graph, some points with liquefaction locating above thecurved line in the left graph were erased in the center graph. It means that liquefaction of oldreclaimed land and natural ground needs stronger shear stress ratio than recently reclaimed land.
Therefore, it is cleared that old reclaimed land and natural ground have higher liquefaction resistancethan recently reclaimed land.
In order to evaluate the influence of age of ground to liquefaction, additional ground surveys andelemental tests are necessary. A map of Koto city in Tokyo Metropolitan as shown Fig. 3 was preparedfor future ground survey. In Koto city, reclamation works starts from the 16th century, and sand boils
were observed in this earthquake and the Great Kanto earthquake of 1923. Total thicknesses ofliquefiable sand layer and silty sand layer up to depth of 10m at boring sites were summarized in Fig.

1 km
NaturalgroundOld
reclamation
land
before 1925

New
reclamation
land
after 1926

Fig. 3 Map of Koto City in Tokyo Metropolitan showing the total thickness of sand or silty sand layer
up to the depth of 10m at the boring site775

3. Amount of data on boring was gathered from web site of the Civil Engineering Center of the Tokyo
Metropolitan Government. But Fig. 3 looks like a contour map, the interpolation between boring sites
makes no sense. The color at the boring sites is important.
Area circled with red line at the bottom and right was area where the most severe liquefaction in
Koto city was observed. The liquefiable layer in the area was thicker than other area. Hence, it isconsidered that the existence of liquefaction was influenced by thickness of the liquefiable layer aswell as the liquefaction resistance. Incidentally, distribution of thickness in Fig. 3 was complex. It islikely to be a result of the complex history of reclamation works (Endoh 2004). Because scale ofreclamation works in the old period was very small, there is a possibility that reclamation material andmethod changed every time. Therefore, locating of the ground survey is very important.
CONCLUSIONS
Amount of data on boring conducted in Kanto region was collected, and relationships between
occurring of liquefaction in the earthquake and SPT N-values were organized. In addition, a map
showing distribution of thickness of liquefiable sandy soil created in order to be applied to future
investigation will be introduced.
a) It is cleared that old reclaimed land and natural ground have higher liquefaction resistancethan recently reclaimed land.
b) It is considered that the existence of liquefaction was influenced by thickness of theliquefiable layer as well as the liquefaction resistance.
c) In order to evaluate the influence of age of ground to liquefaction, additional ground surveys
and elemental tests are necessary. Because of the complexity of the ground, locating of the groundsurvey is very important.
ACKNOWLEDGMENTS
The authors received valuable advice from Professor Tohata of Tokyo University, Professor Kazama ofTohoku University, Professor Tokimatsu of the Tokyo Institute of Technology, Professor Okamura ofEhime University, and Professor Noda of the Nagoya Institute of Technology for this study. Also, theTokyo Metropolitan Government and Chiba Prefectural Government readily provided the data onboring. The Engineering Affair Division and the Kanto Regional Development Bureau of MLIT
supported this research and encouraged us. In addition, our colleagues at the Soil Mechanics andDynamics Research Team of Public Works Research Institute played the major role in conducting
liquefaction assessments. We would like to express our sincere appreciation for everyone involved inthis study.
REFERENCES
Endoh, H. (2004). “Historical review of reclamation works in the Tokyo Bay area.” Journal ofGeography, Vol. 113, No. 6, 785-801.
Japan Road Association (2002). “Specifications for Highway Bridges, Part V. Seismic Design.” JapanRoad Association
JGS (2011). “Geo-Hazards during Earthquakes and Mitigation Measures - Lessons andRecommendations from the 2011 Great East Japan Earthquake.” JGS
Kataoka, S., Nagaya, K., Matsuoka, K. and Kaneko, M. (2011). “Strong Motion and Earthquake
Response Records of the 2011 off the Pacific Coast of Tohoku Earthquake.” Pre-proceedings ofthe 43rd Joint Meeting United States - Japan Panel on Wind and Seismic Effects
Koseki, J. and Ohta, A. (2001). “Effects of different consolidation conditions on liquefaction
resistance and small strain quasi-elastic deformation properties of sands containing fines.” Soilsand Foundations, Vol. 41, No. 6, 53-62
Seed, H. B. and I. M. Idriss (1971). “Simplified Procedure for Evaluating Soil Liquefaction Potential.”
Journal of Soil Mechanics and Foundations Division, ASCE, 97(SM9), 1249-1273.

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