Proceedings of the Eighteenth (2008) International Offshore and Polar Engineering Conference
Vancouver, BC, Canada, July 6-11, 2008
Copyright © 2008 by The International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-70-8 (Set); ISBN 1-880653-68-0 (Set)

Damage of Houses and Residential Areas by Niigata Prefecture Earthquakes (Part2)
Toru Takata
Soil Design Inc.
Tokyo, Japan

Mamoru Fujii
Tokai University
Kanagawa, Japan

Katsuya Matsushita
Misawa Homes Institute of Research and Development Co., Ltd.
Tokyo, Japan

Hirakazu Seki
Kanazawa University
Ishikawa, Japan
has a judgment method based on the SPT (N-value) and the CPT (qc).
In Japan, a judgment method based on the SPT is common. It is a big
factor that a Japanese design system based on N-value is established.
However, it is rare that the SPT is performed for the soil investigation
on housing areas because the SPT is expensive. On the other hand, theCPT is not common in Japan. This cause is in the Japanese groundwhere there is gravel carried by the fast flowing stream river from thehilly district to the estuary. Therefore, soil investigation using the CPT
is difficult in Japan. However, the CPT is economical in comparison
with the SPT and laboratory soil test. In addition, the CPT gives us soil
classification, bearing capacity, consolidation of the ground, and theposition of groundwater level without the sampling of soil. In thisrespect, the CPT is effective in the soil investigation on housing sites.
Most of this investigation is used by the SWS first. Therefore, it isthought that the trouble that a cone cannot be penetrated get fewer
because it can estimate the penetrated power of cone based on the resultof the SWS.

ABSTRACTThe earthquakes of Chuetsu (2004) and Chuetsu offshore (2007) in
Niigata Prefecture, caused liquefaction at many locations, and also
caused damages on the residences and the residential areas due to thefailure of ground. In the future, the judgment of liquefaction on housingsite will become important and it will be thought that the upgrade ofsoil investigation and liquefaction countermeasure is necessary. In
Japan, Swedish weight sounding (SWS) has been widely used in soil
investigation on residential areas. Based on the result of SWS, thebearing capacity of ground can be obtained. However, the judgment ofliquefaction is not obtained.
This paper reports results of SWS, boring investigation, standard
penetration test (SPT), and three component cone penetration test
(CPT) on the housing site which caught the liquefaction damage by theearthquake of Chuetsu offshore (2007) in Niigata Prefecture. In
addition, it reports the applicability of the CPT on the housing site ofJapan.

This paper reports a result of the SWS, boring investigation, grain size
analysis, the SPT, the CPT on the housing site that had been caught theliquefaction damage by the earthquake of Chuetsu offshore (2007) in
Niigata Prefecture. In addition, it reports the current status of theseismic performance evaluation and the applicability of the CPT to theresidential areas of Japan.

KEY WORDS: Soil investigation; cone penetration test; Swedishweight sounding; liquefaction; residential areas.

INTRODUCTION

PLAN FOR GROUND INVESTIGATIONThe Building Standard Law of Japan says that "It is necessary for the
ground with the fear of the liquefaction by an earthquake to confirm
that the harmful damage, transformation, subsidence to the part of abuilding do not produce". It can be said that the examination of theliquefaction is essential because this law is applied to the private
housing without exceptions. The problem of the liquefaction on the
housing sites in Japan is viewed easily from a documentary search suchas "maps for liquefaction sites", because the SWS are common. In
addition, it is difficult to take a liquefaction countermeasure by a
private housing financially, and this is a factor to take a liquefaction
judgment easy.

The investigation place is two housing sites (Kashiwazaki- Matsunami
and Kashiwazaki-Hashiba) that caught the liquefaction damage by theearthquake of Chuetsu offshore (2007) in Niigata Prefecture (Fig. 1).
The magnitude (M) of this earthquake was 6.8; the peak horizontal
acceleration at the ground surface (amax) generated by this earthquake
was about 400 gal. The sand boil due to liquefaction was remarkably
generated on the both housing sites, and differential settlement wascaused in the houses. We investigated the three soundings of the SWS,
the CPT, and the SPT in this both sites. Moreover, the grain size
distribution was analyzed and the soil classification was examinedusing the soil samples obtained from boring holes.

The simple judgment method of liquefaction based on soil investigation

749

Table 1. We used the CPT-cone that can measure skin friction (fs) inaddition to general corn that measured cone resistance (qc) and porewater pressure (u). Moreover, we measured the position of groundwaterlevel by the excess pore water pressure dissipation test of the CPT.
These ground investigation has performed after one month or morepasses this earthquake though it is necessary to examine ideally basedon the result of ground investigation before the earthquake. The SWS
has been done in both residential areas before this earthquake.
Therefore, the SWS have gone again to understand the groundcharacteristic of the earthquake before and after.

HashibaMatsunami

RESULTS OF THE GROUND INVESTIGATION
sea

Figure 2(a) shows each investigation results (boring log, the SPT, theCPT, the SWS) of Matsunami area, and Fig. 2(b) shows one of Hashibaarea. Matsunami area had fine sand of N-value about 10-20 in GL-4.7510.5m. Hashiba had filling sand of N- value about 5 in GL-1.95-4.7m
on the old river. The position of groundwater level was GL-3.3m at
Matsunami area, and GL-3.1m at Hashiba area. The value of eachpenetration resistance distribution of the SPT (N-value), the CPT (qc),the SWS (Wsw, Nsw) shows similar tendency. We obtain measurements
at 1.0m intervals from the SPT, and measurements at 0.25m intervals
from the SWS. On the other hand, the CPT has an advantage that a thinstratum can be detected because we obtain continuous measurements at
0.01m intervals from the CPT. Equation 1 which evaluates N-value
from the SWS results is proposed by Inada (1960).

 3.0W sw + 0.050 N sw
N =
 2.0W sw + 0.067 N sw

(cohesive soil )( sandy soil )(1)

Equation 2 which evaluates N-value from the CPT results is proposedby Saematsu and Suzuki (2005).

 0.340 I c 1.94 (q t − 0.2 )(1.34 − 0.0927 I c ) ( q t > 0.2 MPa )N =
( q t ≤ 0.2 MPa )0Matsunami

In addition, the conversion method of soil classification using the valueof qc, fs, and u is proposed. Robertson et al. (1990) proposes soil
behavior type index (Ic) calculated from the following equation:

HashibaFig. 1. Location of investigation siteStandard
No.
JIS
A1221

Static penetration resistance(Wsw, Nsw)

Cone penetration
test (CPT)

JGS
1435-2003

Cone resistance (qc)Standard
penetration test
(SPT)

JIS
A1219-2001(3)

where Qt is normalized cone resistance ((qt - σvo)/σ’vo), and Fr isnormalized friction ratio (fs/(qt - σvo)). The value of Ic gives us soil
classification shown in Table 2. Moreover, Equation 4 which evaluatesfine fraction content (Fc) from the value of Ic is proposed by Saematsu
and Suzuki (2005).

Examination Value

Swedish weightsounding(SWS)(3.47 − log 10 Qt )2 + (log 10 Fr + 1.22 )2

IC =Table 1. This ground investigation and the investigation standard
Examination item

(2)

FC = I C

4 .2

(4)

Table 2. Soil classification using Ic

Pore water pressure (u)N-value

Maximum grain size
Grain size analysis
Grain size distribution curve
Fine fraction content
Note: JIS; Japanese Industrial Standard
JGS; Japanese Geotechnical Society
JIS
A1204:2000

These investigation methods were based on the each standard shown in

750

Division
No.
1

＜1.31

2

1.31～2.05

sand to silty sand32.05～2.60

silty sand to sandy silt

42.60～2.95

silt to silty clay

5

2.95～3.60

silty clay to clay

6

3.60＜

organic material

Ic

Soil classification
gravelly sandz (m)

Soil Profile

Grain Size Distribution N-value
0

(%)
100 0

50

10

20

qc (MPa)
30

Embankment
1.30

fs (MPa)
20 0

0.1

u (MPa)00.2

Wsw (kN)
0.5

0.4 0

1

Nsw
100

200

300

Silt or Clay

Embankment

2

10

0

Sand
Gravel

2

2

4

4

6

6

8

8

10

10

3.30
4

Gravelly sand
4.75

Depth (m)

6

Sand

8

10
10.50

Silty Clay
12

11.70

12

Clay

14

15.45

Boring Log

SPT data

CPT data

SWS data

Fig. 2(a). The result of the ground investigation (Site: Matsunami area)z (m)Soil Profile

1.95

Clay
Sand
Embankment
Clay

3.30

Embankment
Sand

0.50
1.00
2

0

50

100

0

10

20

Depth (m)

6

8

5.80

SiltyClay
Sand

7.90

Gravel30

100

fs (MPa)
20 0

0.1

u (MPa)00.2

Wsw (kN)
0.4

0

0.5

1

Nsw
100

Silt or Clay
2

Sand

10

2

BoringGravel

4
4.70
5.10

qc (MPa)

Grain Size Distribution N-value

4

4

6

6

8

8

10

10

Clay
12 12.25

14

13.9
14.75
15.45

12

Silty Sand
SiltyClay
Clay

Boring Log

SPT data

CPT data

Fig. 2(b). The result of the ground investigation (Site: Hashiba area)751

SWS data

200

300

The results of the comparison between Ic and boring log are shown in
Fig. 3, and the comparison between fine fraction content based on the
CPT results and grain size analysis are shown in Figure 4, and thecomparison between N-value by the CPT, the SWS and the SPT are
shown in Fig. 5. The soil classification and Fc using the CPT results
was comparatively similar to the results of boring log and grain size
analysis. However, there is a difference in a detailed part of both soil
classification, and there is an enough correlation in rough division suchas gravel, sandy, silt, and clay. Moreover, the results of N-value by the
CPT, the SWS agree with it by the SPT.

area can't be comparable, because the investigation depth (GL-0.25 ~ 0.5m) is too shallow because of the hard embankment. In the result at
Matsunami area, N-value evaluated using the SWS after the earthquake
are smaller than ones before the earthquake. Generally, it is said thatthe ground, which liquefied in the past, increases the liquefaction
resistance, because the wet density increases. This result implies that
there is not the effect of compaction due to the earthquake motion. This
result is only at one area and it cannot be said enough volume of data.
However, there is a case with little compaction effect of earthquake likethis result. We think that the ground that is not equal in density, thetime of the earthquake motion and the residual displacement after theearthquake are related to the factor of this result. Therefore, we thinkthat the ground that has been caused liquefaction due to the earthquake
is a possibility of liquefaction due to a similar earthquake again.

Figure 6 shows the comparison of the SWS results before theearthquake and after it at Matsunami area. The SWS results at Hashibaz (m)Soil Profile

Soil classificationby the CPT

Embankment

Sand

Embankment

Silty sandGravelly sandSilty Clay
Sand
Silty sand

1

Soil behavior type index
(Ic)
2

3

4

Fine fraction content (F C ) （％）

1.30
2

3.30
4

0

2

4

20

40

60

80

Fine fraction content (F C ) （％）

100

0

0

0

2

2

4

4

6

6

20

40

60

80

100

CPT
Grain size analysis

4.75
6

6

Sand

8

10

Depth (m)

8

10
10.50

Depth (m)

Sand

8

8

Silty Clay
11.70

12

10

Clay

14

10

12

12

CPT
Grain size analysis

15.45

z (m)

Soil Profile

1.95

Clay
Sand
Embankment
Clay

3.30

Embankment
Sand

0.50
1.00
2

4
4.70
5.10
6

8

Soil classificationby the CPT

SiltyClay
Sand

7.90

Gravel

1

Soil behavior type index
(Ic)
2

3

Site:Hashiba area

Fig. 4. Comparisons between fine fraction content based on the CPT
results and grain size analysis

4

2

0

4

2

N -value

10

20

30

0

10

N -value

20

CPT

2

ＳＰＴ

SPT

SWS

Sand
Gravel sandSilty sand

SWS

6

4

4

8

6

6

10

30

0

ＣＰＴ

Slty clay
to Clay10

14

Site: Matsunami area

0

Silty sand

5.80

14

CPT

Site: Matsunami area

Depth (ｍ）

Boring Log

Depth (m）

12

8

8

Clay
12 12.25

14

13.9
14.75
15.45

Silty Sand

10

10

14

12

12

Silty sandSiltyClay
Clay

Boring Log

12

CPT

14

Site:Hashiba area

14

Site: Matsunami area

Fig. 3. Comparisons between soil classification based on the CPT
results and boring log (reference table.2)

Site:Hashiba area

Fig. 5. Comparisons between N-value by the CPT, the SWS and the
SPT

752

N- value
0

10

20

30

40

50

0

0

2
0

2

2

4

4

4

6

6

6

before earthquake
after earthquake
Ave(before earthquake)
Ave(after earthquake)

F L -value

0

0

1

2

8

Depth (m)CPT

Depth (m)

8

10

10

12

Fig. 6. Comparisons of the SWS results before the earthquake and after
one at Matsunami area

CPT

8

12

SPT

14

COMPARISON BETWEEN THE JUDGEMENT METHODOF LIQUEFACTION USING CPT AND SPT

SPT

10

14

Site: Matsunami area

Site:Hashiba area

Fig. 7. The depth distribution of FL on input earthquake condition(M:6.8,amax:250gal) used to design generally

The method of judging liquefaction is the detailed one and the simple
one, and this research used the simple method. The outline is shown as
follows:

0

Depth (m)(a) Detailed judgment method
The liquefaction resistance ratio (R) is measured from the results ofcyclic triaxial test using the undisturbed sample obtained in situ, andthe cyclic shear stress ratio (L) is obtained from seismic response
analysis etc. Thus, we obtain the liquefaction safety rate (FL (: R/L)).
(b) Simple judgment method
The liquefaction resistance ratio (R) is converted from the results ofground investigation or laboratory test, and the shear stress ratio (L) is
calculated from the design earthquake motion. Thus, we obtain theliquefaction safety rate (FL (: R/L)).
The liquefaction resistance ratio (R) in any depth can be converted fromsome methods. Recommendations for design n of building foundations
issued by Architectural Institute of Japan (2001) shows the following
two methods as a method with high reliability.

F L -value

1

2

0

0

0

2

2

4

4

6

6

Depth (m)2Depth （ｍ）

F L -value

1

8

10

1) Method of presuming R based on the SPT results (N-value) andthe grain size analysis results (FC).
2) Method of presuming R based on the CPT results (qc, fs and u).

12

2

CPT

SPT

8

10

CPT

SPT

14

12

14

Site: Matsunami area

The cyclic shear stress ratio (L) is calculated from the following
equation:F L -value

1

Site:Hashiba area

(5)

Fig. 8. The depth distribution of FL by value on the earthquake of Chuetsu
offshore (2007) in Niigata Prefecture (M:6.8, amax:400gal)

whereτd (stress reduction coefficient); σz and σ'z (total and effective
vertical overburden stresses); g (acceleration of gravity); amax ( peakhorizontal acceleration at the ground surface generated by theearthquake): rn(correction coefficient to cyclic count(=0.1(M-1); M =magnitude)): rd (decrease coefficient (= 1 - 0.015z; z = depth (meter))).
Figure 7 shows the depth distribution of FL on input earthquake
condition (M: 6.8,amax: 250gal) used to design generally. Figure 8
shows the depth distribution of FL by value on the earthquake of
Chuetsu offshore (2007) in Niigata Prefecture (M: 6.8, amax: 400gal).
The depth distribution of FL based on the CPT results and based on the

SPT and the grain size analysis results are roughly corresponding
though FL based on the CPT results is a little smaller than it based on
the SPT and the grain size analysis results. There is little liquefied layer(FL <1.0) at the design condition on both areas (Fig. 7). On the other
hand, when the earthquake condition measured in this time is given, theliquefied layer on Hashiba area is calculated GL-3~-7m, and it on
Matsunami area is calculated GL-3~-10m(Fig. 8). The sand boil isgreatly generated due to the liquefaction on this earthquake in bothhousing areas. It can be said that FL shown in Figure 7 almost agrees
with this phenomenon.

L=

τd
σ
a
= rn max z rd
g σ 'zσ 'z

753

(c) Evaluation method using the relation of two-layer ground (theliquefied layer and the non-liquefied layer( U.D.Co., 2003)
Collected N-value increase ( ⊿ Nf )EVALUATION OF THE LIQUEFACTION INFLUENCE IN
THE HOUSING
The damage of the housing caused by liquefaction becomes at theposition of the liquefaction layer that is thick and shallow remarkable.
The damage of the foundation and the housing is different in the level,
the thickness, the depth of the liquefaction layer etc. Moreover, it is not
related to the damage of the housing and the residential area
immediately even if the liquefaction layer is in the ground. Therefore, itis necessary to evaluate the influence that liquefaction gives the
housing. In this research, the three evaluation methods of the influence(a, b, c) that liquefaction gives the housing in the flat ground are used.
The methods are shown as follows.

10
8
6
4
2
0
0

10

20

30

40

Fig. 9. Relation between Fc and ΔNf
0.6
0.5（1－FL ≧ 0）

(6)
0.4

τ d/σ' ｚ

Table 3 shows the liquefaction judgment division by PL according to
the liquefaction region-zoning manual (1998).

0.3
0.2

Table 3. The liquefaction judgment division by PL

γcy＝8％
γcy＝4％
γcy＝2％

0.1

Liquefaction
extent of the
impactPL-value

γcy＝1％
γcy＝0.5％0

Small

Middleground motion
0≦PL≦5Large
ground motion
0≦PL≦5Large

5＜PL≦15

5＜PL≦20

Huge

15＜PL

20＜PL

0

10

20

30

40

Collected N -value (N a )Fig. 10. Relation between Na, γcy and τd/σ’z
Table 4. Relation between Dcy and the damage level of liquefaction
Dcy (cm)(b) Evaluation method by the dynamic surface displacement (Dcy)(A.I.J., 2001).

Liquefaction extent of the impact

0
5
5-10
10-20
20-40
40

The dynamic surface displacement (Dcy) is proposed as one index thatshows the relation between the dynamic horizontal displacement of theground surface caused by liquefaction and the damage level of the
housing. It depends on the following procedures when the CPT result is
used.

None
Minor
Small
Medium
Large
Huge

10

Liquefaction layer thickness ( H 2 (ｍ))1) N-value converted by the CPT results (Eq. 2) is treated as N-value by
the SPT results.
2) Corrected N-value (Na) to Fc and σ'z is calculated from Equation 7.

N a = N 1 + ∆N f

50

Fine fraction content (F c (%))(a) Evaluation method by the liquefaction index (PL) (N.L.A., 1998)
The liquefaction index (PL) is proposed as one index that evaluated theinfluence that liquefaction gives the housing. It is calculated from thefollowing equation:

PL = ∫ 020 (1 − FL ) ⋅ (10 − 0.5 z ) dz

12

(7)

where N 1 = corrected N-value concerning confining pressure( N1 = 98 σ z' ⋅ N ):∆Nf = corrected increment value concerning Fc
shown in Figure 9.
3) Cyclic shear stress of the both depth corresponding to Na and τd/σ'z(γcy) is presumed from Figure 10.
4) It is assumed that γcy of the each depth is generated in the same
direction. And, γcy is integrated into a vertical direction. And, themaximum horizontal displacement by integrating γcy into a verticaldirection is obtained.
5) The maximum horizontal displacement is treated as the dynamic
surface displacement (Dcy). And the influence that liquefaction gives
the housing is evaluated to the value of Dcy shown in Table 4.

9Large groundmotionMiddle groundmotion8
7
6

A liquefaction

5
A liquefaction

4
3
2
1
0
0

1

2

3

4

5

6

7

8

9

10

Nom-liquefaction layer thickness (H 1 (ｍ))

Fig. 11. The borderline of liquefaction in relation between H1 and H2
The clay soil or unsaturated soils that is shallower than the position ofgroundwater level are the soil layers where the possibility ofliquefaction is a little. Therefore, even if the saturation sandy soil undergroundwater level is caused by liquefaction at the earthquake, it might754

not influence the housing area and the housing by non-liquefied layeron the surface ground. Figure 11 shows a borderline of liquefaction in
the both earthquake motion. This plotted points in Figure 11 gives us
the presence of damage by liquefaction. Table 5. shows the evaluation
result of the influence that liquefaction gives the housing using method
1-3. It is calculated that PL= 0.0 ~ 1.2 (Matsunami), PL= 0.0 ~ 1.1(Hashiba), Dcy= 0.0 ~ 1.0 (Matsunami), and Dcy= 0.3 ~ 1.5 (Hashiba),
and it can be said that the influence by liquefaction on the housing is alittle in the design earthquake condition (amax= 250gal). However, it iscalculated that PL= 9.0 ~ 16.7 (Matsunami), PL= 12.9 ~ 16.2 (Hashiba),
Dcy= 10.2 ~ 15.3 (Matsunami), and Dcy= 7.6 ~ 11.5 (Hashiba), and it
can be said that the influence by liquefaction on the housing is verylarge in this seismic condition. In addition, the evaluation method using

the relation of the non-liquefied layer and the liquefied layer of theground surface gives us the similar result to method 1and method 2.
Thus, we obtained an almost similar result by three methods. Moreover,an obviously different results in case of design condition and this timeearthquake condition is obtained. We thought that the liquefied layer
became remarkably thick because this earthquake motion is larger thanthe earthquake motion using the designs. The layer that changes into
the liquefied layer by the difference of this earthquake motion isthought to be sand layer of N-value 15~20.

CONCLUSIONSThis paper reports a result of SWS, boring investigation, standard
penetration test (SPT), and three component cone penetration test
(CPT) on the housing areas that had been caught the liquefaction
damage by the earthquake of Chuetsu offshore (2007) in Niigata
Prefecture. As a result, the following conclusions were obtained.

Table 5. The evaluation result of the influence that liquefaction gives
the housing
Site:Matsunami area
Earthquake
GroundemotionInvestigation data
Method
SPT,FcM
amax
CPT
P -value
1.2
0a L
Judgment
Small
Small
D
1.0
0
250
b cy
Judgment
Minor
None
gal
H1 (m)
5.8
c H2 (m)1.50Judgment
OKOK
6.8
PL-value
16.7
9.0
aJudgment
Large
Large
D
10.2
15.3
b cy
400
Judgment
MiddleMiddlegal
H1 (m)
3.7
4.15
c H2 (m)6.5
6.0
JudgmentNG
NG
Site:Hashiba area
Earthquake
GroundMethodemotionInvestigation data
SPT,FcM
amax
CPT
PL-value
1.1
0.02
aJudgment
Small
Small
Dcy
0.3
1.5
250
b
Judgment
Minor
Minor
gal
H1 (m)
5.2
12.2
c H2 (m)0.8
1.0
Judgment
OKOK
6.8
PL-value
12.9
16.2
a
Judgment
Large
Large
Dcy
7.6
11.5
b
400
Judgment
Small
Middlegal
H1 (m)
4.6
4.2
c H2 (m)3.6
5.0
Judgment
NG
NG
Note: NG; A-liquefaction OK; Non-liquefaction(a) The judgment method of liquefaction by the CPT results wascompared with the judgment method by the SPT and grain size analysis
results. It has been obtained a result similar to both though it is a simple
method. In addition, these judgment results were able to explain the
housing damage and the boil sand caused by an actual liquefaction.

Reference
Table. 3.
Table. 4.

(b) It was observed that the maximum horizontal acceleration waslarger than the designed acceleration used in general, and the value ofseismic intensity scale is strong with 6+. Therefore, it has been
understood that the non-liquefied layer in the design condition became
a liquefied layer because of this earthquake condition.

Fig.11
Table.3.

It is necessary to establish the soil investigation of private housing thatused by the judgment of liquefaction in Japan. It may be said that the
CPT is the investigation method that is influential at the point where
there is easily a liquefaction judgment. We think that it will benecessary to suggest a ground improvement method of housing sites
aimed for liquefaction countermeasure as well as investigation methodin future.

Table. 4.
Fig. 11

Reference

REFERENCES

Table. 3

Inada M. (1960),“Interpretation of Swedish weight sounding”, Monthly
Magazine of Japanese Geotechnical Society, Vol.8, No.2, pp.13-18.
Saematsu T and Suzuki Y(2005),“Correlation between CPT data andsoil characteristics,Part1:Evaluation of soil classification and SPT Nvalue”, Japanese Geotechnical Society.
Robertson, P.K. (1990), “Soil classification using the cone penetration
test”, Canadian Geotechnical Journal, Vol. 27, No. 1, pp.151-158.
Architectural Institute of Japan (2001), “Recommendations for designof building foundations”.
National Land Agency (1998), “The liquefaction region-zoning
manual”
Urban Development Corporation (2003),“A seismic design manual on
residential area (a plan)”, pp.36-38.

Table. 4
Fig.11
Table.3
Table. 4
Fig. 11755