Soil Liquefaction Potential Evaluation with Use of the

Soil Liquefaction Potential Evaluation with Use of the
Simplified Procedure
T. Iwasaki and K. Tokida
Ground Vibration Division, Earthquake Disaster Prevention Department, Public Works Research
Institute, Ministry of Construction, Tsukuba Science City, lbaraki-ken, Japan
F. Tatsuoka
Associate Professor, Institute of Industrial Science, University of Tokyo, Tokyo, Japan
SYNOPSIS
A simplified method based on both a liquefaction resistance factor, FL and a liquefaction potential factor,
PL has been proposed for evaluating soil liquefaction potential. The factor FL indicates the liquefaction potential at a
given depth of a site, and the factor PL indicates the one at a site. The effectiveness of the proposed method is investigated by calculating the factors FL and PL at both liquefied and non-liquefied sites during past typical earthquakes
in Japan, and carrying out shaking table tests.
INTRODUCTION
As a result of various and detail studies on the liquefaction
of sandy soils, several simplified and complex methods
have been proposed to evaluate the liquefaction potential.
The authors, Iwasaki et al. (1978), proposed a simplified
method with use of a liquefaction resistance factor FL
and a liquefaction potential factor PL • Based on the
simplified method, the liquefaction potential of sandy soils
can be estimated from its N-values, its unit weights, its
mean particle diameters, and the maximum acceleration
at the ground surface. In this paper, the simplified
method is described and to prove the effectiveness of the
method, the factors FL and PL at 64 liquefied sites and
23 non-liquefied sites during past various earthquakes
are calculated according to the proposed simplified
method, and also the factor FL is calculated for the
model ground in the shaking table tests on soil liquefaction.
where N is the number of blows in the standard
penetration test, Ov' is the effective overburden
pressure (in kg£ /cm2), and Dso is the mean particle
diameter (in mm). L in Eq. 1 is the dynamic load
induced in the soil element by a seismic motion,
and can be estimated by
asmax
Ov
(3)
rJ/
g
where 'max is the maximum shear stress (in
kgf/cm2),
<Xsmax is the maximum acceleration at
the ground surface (in gals), g is the acceleration
of gravity(= 980 gals), avis the total overburden
pressure (in kfg /cm2), and rd, the reduction factor
for dynamic shear stress, accounting for the deformation of the ground. In 1971, Seed and Idriss proposed a
relationship between rd and depth. However, in this
paper, the relationship,
SIMPLIFIED METHOD
In the proposed simplified method an ability to resist the
liquefaction of a soil element at an arbitrary depth can be
expressed by the factor of liquefaction resistance (FL).
R
00
]
( 1)
L
N
.J:
a.
where R is the in- situ resistance (or undrained
cyclic strength) of a soil element to dynamic loads
and can be simply evaluated, based on undrained
cyclic shear test results, as follows :
for 0.04
R
~
7IU1l •
0.0882
R = 0.0882
D,o ·
0.6
~
J07+Q? +
A
Oy'
N
+ 0. 7
0.225 log
- 0 05
.
10
D;;
F~
W(z)
2.0
10
5
5
10
10
15
15
20
20
Cli
a
TIUII
0.35
.
(b)
(a)
(2a)
(2b)
Fig. l
209
Integration of FL
210
rd
=l
- 0, 0 15 Z
Nishi
(4)
Oh- hat a
D5o
0I
where Z is the depth in meters, is used,
02
o---o
0 0
10
It is obvious that the damage to foundations due to soil
liquefaction is considerably affected by the severity of
liquefaction, As only the ability to resist liquefaction
at a given depth can be evaluated by FL , an index of
liquefaction potential, PL, can be introduced to express
the severity of liquefaction as,
Cho
(mml (
20
30
Ni igata
City
el'ltimsted )
05
N( after
in
I0
earthquakt•)---...
40 50 0 0
FL
I0
20
ks' 0 17
r, oJ-0.015Z
--¥=
(5)
$
N
----~
in which F = l - FL for FL
1,0 and F = 0 for FL > 1,0
as illustrated in Fig, l(a), and W (Z) = 10- 0,52 (Z in
meters), as illustrated in Fig, l(b), For the case of
FL = 0, 0 for the entire range from Z = 0 to Z =20m,
PL becomes 100, and for the case of FL
1,0 for the
entire range from Z = 0 to Z = 20 m, PL becomes 0, 0,
I0
tJ
t
050
+
I
}
15
CASE STUDIES OF PAST VARIOUS EARTHQUAKES
Kuribayashi et al, (1974) accumulated data on liquefaction
observed during past 44 earthquakes in Japan, and made
clear the distribution of liquefied sites and damage of
structures due to liquefaction, Furthermore in 197 8
liquefaction was observed at about 30 sites during the
Miyagi-ken-oki Earthquake (Iwasaki et al, (1980) ),
Both the liquefaction resistance factor, FL and the
liquefaction potential factor, PL were calculated for
liquefied sites and non-liquefied sites where geotechnical
information was available, during each of the following 6
earthquakes : the Nobi Earthquake ( 1891), the Tonankai
Earthquake ( 1944), the Fukui Earthquake ( 1948), the
Niigata Earthquake ( 19 64), the Tokachi-oki Earthquake
(1968) and the Miyagi-ken-oki Earthquake (1978).
Calculations were made for 64 liquefied sites and 23 nonliquefied sites, The geotechnical and seismic data at the
sites are summarized in Table l,
Fig, 2
Relationships between FL and Z at the NonLiquefied Site
Shows Bridge in
Nii~ata
City
(Bori~
Not)
Dso lmml
01
02
c:--<>
0 0
10
10
05
( a f tf"r ear thcpake) --.......
20
30
40
50
00
I 0
20
*
§
N
Figs, 2 and 3 show the typical variation of FL with depth
at a liquefied and a non-liquefied site, respectively. It
can be seen that FL is, in general, less than 1,0 in the
liquefied layers, and greater than l, 0 in the non-liquefied
layers, The tendency of FL at other sites was similar,
FL
ks' 0.17
r, 'i-0.015Z
----
Fig, 5 summarize the calculations of FL with depth at all
liquefied and non-liquefied sites in Niigata Earthquake
(see Table 1), The liquefied layers shown by black dots
in the figure were estimated based on damage to structures (see Fig. 3). It can also be seen that FL is mainly
less than l. 0 in the liquefied layers and the liquefied
layers are mostly located at shallower depth than 10 m,
10
----- Dso
~~>X
''
X
15
* lL is estimated from
Fig. 3
the damage to piles
Relationships between FL and Z at the
Liquefied Site
Geotechnical Data at Liquefied Sites and Non-Liquefied Sites
(B) Non-Liquefied Sites
Table 1
Liquefied Sites
(A)
Sot!
Data
Earthq.ldke
S1te
No,
Deptn of
WHer Table
D5o
~-Om
M
_
MaJor SoLI Type
Fme to Me<l. Sand
2.)
M
0. 3
£,:-.1
2.<;
M
"
0. 0
--
Jtndoji
K-~-g~ne-.-~-ho
4
-: -~:~~~;;~ho-
20.2
18.3
Br. 5
0.0
E.~
39.3
Br. 7
0.0
E,M
lb.l
Br.!.
0.0
Br. l
1.50
"
"
0.0
0. 0
E
Br. 2
0.0
"
"
l:lr.3
~Lt'o)ata C1ty
:'\ 1 q~a t"
0.0
,
L9o-l,
M:7.S
Br. 2.
o.o
B
Br. 3
19.6
l,l>j
Br.l
Br. 1
Br. 2
Br. 3
l. 2 ~
BCll-2
~--~~---···-·
14.3
~--<
ll. 7
\1
C'Jarse Sand
2.8.6
"
"
"
"
·"
fu1e Sand
20.1
5.8
F1ne to Med. Sand
-~~-----
13.3
F1ne S«nd
20.1
~
G.fe~
Prei.
l ~''l'
M;:;~,
Ctty
l'"H.O,
M=:~.
F U.u,
45
__ 4_~ __ i__Ma_~~ka :-.lo.Z
Pref.
47
j
Gravelly Sanr:!
M
"
0.9
0
48
J
Morth o[ Ab:lklHT\.1
YurLa_g_e_~k_amL
49
50
Yurtage Br1r:lge
__
M~7.
56
57
T
M~7.
2.4
4
Uomao;;hi
Estimated from Damage to Structures
2.~7--~ (!J
6
36_._~
Recorded Value at Hachinohe
Estimated by the Empincal Equation for Alluv1al Deposits (
Estimated by Using Fq;:. 4
Esttmated by Dynam1c
'"
BRI (19651
K1shida {1970)
U,l
18)
Yasur:la et al. 11980)
~and
Co<>r~.-
~er:!.
~
------
S.on-1
::. .. nr:lv Slit to Mecl. Sand
eta, to
5
173
Co"r~e S.!.r~d
Sand
180
20.-1
180
10,3
180
9.9
11:15
1.0
185
fi
o.
~
185
~
.! l.
~
190
210
6
ZIO
:vlc·l. to :>dty Sand
• Cldy to Coarse Sand
~
2.30
6
ns
61 -1----
:\u.l
0.0
62
:\·4
0.5
.\1
1.3
M
fme to Coarse Sand
~
1-1.1
?.7.1
as
6
11:1.2
1!:10
fi
12.3
11:10
6
5,6
·----
S·lt to ftne Sane!
36.?
185
125
Sdt to Me<:!. Sand
4.1
4.1
23 0
f'tne ""n-1
- ;, .. ..,..jy
Analyses of Ground
Reference
Ohashtetal. (19771
::.ar~d
~~!sponse
BRI 11969)
fme toM<·!. :.and
A
l
Japanese Soc1ety of CIVil Eng1neers
0.0
!
'
I
295--t--i·l~-,-
and !3-Z
Estlmated from Recorded Value at Other S1tes
(6)
(31
0.0
W-G
M
! Sdt to Med. Sand
I
'
'
~~
:
1
0. 0
j
18.7
~
j
t
M
t-;
295
.~
E
,
M
4. }
---1-M
~-S•l~_y_to~~Sand_+~
1 -Fin~-~~~~
-~--~~:;
(2)
..... _,
4
7
v.
~toCoarseSand
·
180
--·. -·--·· ..----+--Slit to Silty Sand
: Me d. to
;·M- ;-
Co~-rs; Sa-n~
195 ,6
-
(J)
(8}
t--m-:;
I
Fme Sand to Clay
'·'
0.0
Sandy S1lt to Gravel
Med. to
Stlt~_Sand
17.1
0.0
F'tne to
~ed.
Sand
3.7
--'
I
N
B~l
Ka.wagishi~Gho
(I)
~o.l
:-.-5
Recorded Value at
{21
:"<o.l
"
1
4. 0
8.0
M: Measured
19.5
"
I Wabucht
F1ne Sand to Silt
~_:~.:_6_j
~
4. 6 I
1- - +
~
I
I
Fme to Mt-d. Sand
M
1
A : So1l Data after Earthquake
2.3.7
Shtomi
--
~4
0.90
3,l5
Z70
59
63
1
'-'
60
-------+----------
A
.,
210
!.72
::-lakamura
I
170
uu~t~;;;-~;_;-;:-;:;-;;;:,;.0;•---i ·'"- .._1
2.50
;
13.0
:\o.l?.
---+---------
~
-:----L~-3~~-
13
ll_Q
~~- -~-rhfu
__ ___,___
I
(71
.\i"t·~.
0.0
'
A
0.85
3,9
Compacted by Sand Compaction Piles, near Uornachi
ll.-1
\.lecJ. to
"
"
E
I M_t' :m_e -~~.=dty Sand
4. 3
M1yagi-kenOk1,
1978,
M=7.4
I
Estunated by Vs1ng Table 2
~~
• :>andy s,l\ to
0.?.6
~7
M1yag1 Pre!.
B: Soil Data before Earthquake
E
(ll
J.S.S.M.f.E. (19761
Ftn" to Mt··i. ;,ancJ
0.
0. I
~ed1um Sand
E
I
__;
·-
(51
(6)
M
9.3
I Wabuchi
l·L'l
<.7
l17'i,
A-2
31')
:\o.l
MIYil'll-kcn·
0. 0
1.8
;o..;o.Z
.\1.--: . .">an-:: to Gr,.,,·e!
F,n._. to
Ok1,
toCoarse~~~-d-~
FtneSand
.l-
A·l
Uomach1
Ishihara (1976)
.)dt to Coarse
Pre!.
: MtnamiSendal
{51
~
\i•J.2
55:
23
'Med.
I ...
~~
~----·
{4)
\{
~l.!Y"O:'
20
21
M
M
Br. 2
17.7
~5
'\o,i
;\lo.l
a.1
~~
Yama;.akt
! Otri (IJ
-+-
EaL Bndge
32;
l.
1.3
-+
r, .....'>«nd
0.
2
" l
·o Coarse :::ian'!
!•.)
Y·Z
~o.
Br.1
2.6.3
• Y-l
)(o.)
Abukuma Brtdge
zoo
;,and
C"J.l.T»<'
o.o
- -+--
3
.\l!"dl-J!ll S<1nrl
C?arse Sand
.J
52
53
to Grav. Sand
4.?.
R1ve:
51
54
~and
;,,:v.-
O.!l
FcllH.a,
\1
Abuk"ma Br~~-~--- ----~-
235
0.7:;
1.2
-~~-
-~52_____4___ ...
Med•urr1._S_and
-~~_L Ta_~~y_a l-16':1
46
"
().9
O.o
17
... )._~---- ---
--
t.l
0
l"onank-<>,
:--/a~o)'a
zoo
-----·-·-
:-;Obi,
Pg
---~~?-
fme Sand
-··
0.95
O.:i7
Ktnnou Budge
5.1
9. 7--
----~~-
Tokacht·Ok•,
19611,
M=7.9
:--laton Rtver, 3.2 Km
22
1._3_3------~--F'~? ~d. Sand ----~- _ _ -1_._:1
!lakodate
Ctty
15
~:.-_'_':,~_to.Coarse~.~n_d__j
l.l
3. 5
~--o.ol
1
1
16
0.0
f1ne Sand
0.0
A
l
Yunage-kami
Kttakaml R1ver
E
I Rei.
P,
(gall
I
~---
I
14
MaJor Soil Type
18.9
Mer:hum Sand
l:lr.l
~-a-~~-ya
"'
~-
Br.Z
:
'
14.5
1.2
BCI1
~
:\akamura
13
19
-~-~~-
C0arse Sanrl
-~~-~~.:!.
+
(-1)
10.5
_______1:2.
BCZI-l
'
..
--r
A
,___
j A
12
16.5
110
A
I
:::;,
Br.l
11
28.2
Coarse Sand
\led. to Coarse Sand
~
0.63
Gotanda Bridge
I
2.3m
2.5 ____
~-~
Ni•gata,
1964,
M=7.5
fuku1,
1948,
M«7.3
13.1
Br.Z
l:lr.l
8
23.2
'-'
Br. l
City
32.9
Coarse Sand
Q. 0
'·'
o.;,
~iigata
1
(3)
,
Dso
l -~-·'----~--~-~---+---M·~~J.~:ns~
~--s
Br, 5
2-1.0
Med. to Coarse Sand
M
Sr. L
1
A
1.~
~---~
0.6
-----~~~-
_..,_ __Br.!.
.
• Bn
, "'.l_j
Mats~a~--·---~--~
+-Shtn
'
-~---~
H•gash 1 Kosen
1.3
Soil
Depth of
Data i Water Table
Site
5.8
ftne to Me d. Sand
E, '-1:
;\lo,
9.0
~1
0. 0
Rel.
24.'J
Fu'l.C to Coarse Sand
-------
2.5
P,
(gal!
(1:1)
212
Table 2
Average Values of the Unit Weights and Mean
Particle Diameters of Different Type of Soil
(This table was used only when these values
were not tested)
Unit Weight,
lt( t/113)
Soil Type
Fe
Mean Particle
Diaaeter, Dso (-)
Surface Soil
1.7
0.02
Silt
1. 75
0.025
Sandy Silt
1.8
0.04
Silty Sand
1.8
0.07
Very Fine Sand
1.85
0.1
Fine Sand
1.95
0.15
I:
....
a.
UJ
0
Mediua Sand
2.0
0.35
Coarse Sand
2.0
0.6
Gravel
2.1
2.0
<lJ
u
~
200
...
:::J
(./)
100
Fig, 5
Relationship between FL and Z at the Liquefied
and Non-Liquefied Sites during Niigata Earthquake
"'0
c
~ 50
(.9
Fig, 7 summarize the calculations of PL at all liquefied
and non-liquefied sites in Table 1, i,e,, both relation
between number of case and PL and relation between
accumulative percentage of PL and PL, According to
Fig, 7, it is found at non-liquefied sites PL is less than
20 and the probability that PL is less than 5 is 70 %, on
the other hand at liquefied sites the probability that PL
is less than 5 is only 20 %and 50 %of the sites range
more than 15, Based on the above results, the assessment for soil liquefaction potential using PL can be clone
as follows,
~
;:n
c
.Q
;:n
...
<lJ
a;
20
10
~ ,_~lion USod
5
(Kuribayasht &
Iwasaki ,1980)
u
u
<{
E
:::J
E
x
Ill
~
Measured Value
2
30
50
100
200
Liquefaction potential is very low and
detail investigations on soil liquefaction
aren't needed in general,
500 1000
IJ (km)
Epicentral 01stance,
Fig, 4
Relation between Maximum Acceleration at the
ground surface,
ftsmax , and Epicentral Distance, L1, during the Miyagi-ken-oki Earthquake
Fig, 6 shows the frequency and accumulative incidences
of FL values for both liquefied and non-liquefied layers
at all sites in Table 1" Hereupon the liquefied layers
were estimated based on damage to structures or if not
estimated by soil conditions, i, e,, the saturated sandy
layers whose N-value is less than 15 and whose D_, 0
ranges from 0,02 mm to 2,0 mm were regarded as
liquefied layers, The distribution of FL at liquefied
layers is very different from that at non-liquefied layers,
At liquefied layers most (about 87 o/o) of FL values distribute in the range less than 1,0, and while at non-liquefied layers most (about 89 %) of FL values distribute in
the range more than 1,0, However it must be noticed
that about 13 % of FL values exceed 1, 0 at liquefied layers
and about 11% of FL values indicate less than 1,0 at nonliquefied layers,
O<PL
5 ---
Liquefaction potential is low but detail
investigations on soil liquefaction are
needed only for specially important
structures.
5<PL
15 --
Liquefaction potential is rather high and
detail investigations on soil liquefaction
are needed for important structures and
countermeasures of soil liquefaction are
neededed in general,
----
Liquefaction potential is very high and
detail investigations and countermeasures on soil liquefaction are needed,
15
< PL
As mentioned in the above, it has been shown that the
liquefaction potentional factor PL may be used to assess
the liquefaction potential at a certain site reasonably,
Moreover the nee es sity for detail investigations on soil
liquefaction also can be judged based on the factor pL
calculated by the proposed simplified method,
213
~
~
3.0
Depth
Estimated Liquefied Loyer
0
!
0
H
2.5
20
2.0
2.5
0
30CM
60CM
BOCM
0
0
6
0
0
0
0
~
0
t==·;iJ~g
~
20
0
100
~
0
3.0
~
0
~
ll
lO
Oi
5
15
-'
c
'"'
"-
~
-l
<l
10
10
j
""
~
00
0.5
1.0
1.5
2.0
25
~
&
3.0
"'
FL
0
0
Fig. 6
Distribution of FL Values and Their Accumulative Incidences, in Percentage, Comparing
Liquefied Sites with Non-Liquefied Sites in
Table 1
Non-Lq.Jefoction
ELAPSED TIME ISEC.I
Relationships between Pore Water Pressure
and Acceleration of Non-Liquefied Sand Layers
and FL Values in Shaking Table Tests
Fig, 8
Uquefoction
(•4)
·~~~~~~~~~
~
§
0
!
~
~
~
~
0~-L~~--~~~~~~~~~~~~~~~~~~~
.~
"5
10
~
j
50
~
~
a
;j
30
0
100
Depth
0
('%)
Fig. 7
~
Distribution of PL Values and Their Accumulative Incidences, in Percentage, Comparing
Liquefied Sites with Non-Liquefied Sites in
Table l
SHAKING TABLE TESTS ON FL
H
[ 30CM
60CM
BOCM
l==
0
20
-'
"-
~~
' cig
;J'U
100
8
15
100
~
:::::
<:
0
g.
!?
:30
~
------------
1.0
50
"'
<l
'lS
~
§
~
;_
""
~
l;
l
~
I?
,.. .••../,
~
80
Fig, 9
0
0
a;
"i
i
ELAPSED
Figs, 8 and 9 shows the relationships between ground
acceleration, pore water pressure and FL for nonliquefied and liquefied test, respectively. In these
figures, FL values were estimated by equations (2) and
(3) based on test results,
It can be seen that according
to the increase of pore water pressure, FL values decrease to less than 1.0 in the liquefied layers (see Fig, 9)
and on the other hand FL values are more than 1, 0 in the
non-liquefied layers (see Fig, 8),
~
0
0
flo
The authors carried out shaking table tests to clarify the
effectiveness of FL for assessing liquefaction potential of
sandy soil. A loose saturated sandy ground model with
about 0, 95 m depth, 6 m length and 3 m width was prepared on shaking table and shaked by sinusoidal wave,
The frequency of the inputted motion was 7 Hz and the
magnitude of the table acceleration ranged from 30 gals
to 250 gals, The acceleration and pore water pressure of
ground model during shaking were measured,
0
0
TIME ISEC.I
Relationships between Pore Water Pressure
and Acceleration of Liquefied Sand Layers
and FL Values in Shaking Table Tests
214
Fig, 10 summarize the relation between F L and the rate
of ground liquefaction, du/ <Jv' ( du: an excessive pore
water pressure, Ov' an effective overburden pressure)
for liquefied layers, FL decreases according to the
increase in du/ oy', and on the average FL is less than
1.0 when,JU/Ov'is more than 0,5 andwhendu/ov'is 1,0,
i, e,, the sand layer liquefy perfectly, FL decreases to
less than about 0, 6.
As mentioned in the above, it's been clarified in these
shaking table tests that FL is adequately equivalent to
the liquefaction phenomena and may be used to estimate
the soil liquefaction potential of saturated sandy layers,
I
0
I o
\
0
\
0
\
\
\
~
o\
~~
1.0
co
\
\
ob,
'
0
0
0
~---0
0
0.8 -----~---..;:..:.-~.:..--o-
--
__o_o_g~-~~
_':-.._ ____f!__
~
-:--0-----
__
Kishida, H. (1970), "Characteristics of Liquefaction of
Level Sandy Ground during the Tokachi-Oki Earthquake", Soils and Foundations, Vol.X, June, No.2,
0
0.6
Fig, 10
Japanese Society of Civil Engineers, "The Report on the
Damage during the Niigata Earthquake of 1964" (in
Japanese),
Japanese Society of Soil Mechanics and Foundation
Engineering ( 197 6), "Report on Earthquake Damage of
Subground Streets and Structures, "March (in Japanese),
oo '.......,
,o
BRI ( 1969), "Investigation on Liquefaction of Saturated
Sand and Some Problems on Soil-Structure-Interaction,
"The Building Research Institute, Ministry of Construction, No, 55 (in Japanese),
0
d\
00
0
BRI (1965), "Report on Damage to Building during the
Niigata Earthquake, "The Building Research Institute,
Ministry of Construction, No, 42, 1965 (in Japanese),
Ishihara, K, (1976), "Report of Liquefaction Tests of at
the Site of Shinanogawa Water Gate, "Report to the
Hokuriku Regional Construction Bureau, the Ministry
of Construction (in Japanese),
If
0
REFERENCES
Relationships between FL Values and the Rate
of Ground Liquefaction du/ Ov' in Shaking Table
Tests
CONCLUSIONS
The simplified method based on the liquefaction resistance factor, FL and the liquefaction potential factor, PL
proposed to assess the liquefaction potential was investigated by calculating the factors at 64 liquefied and 23
non-liquefied sites during past 6 Earthquakes in Japan
and shaking table tests, From these studies, it was
found that most values of FL are less than l, 0 at liquefied
layers, and are larger than 1,0 at non-liquefied layers,
Further, the values of PL and their incidences at liquefied sites differ from the ones at non-liquefied sites.
Therefore, the liquefaction potential can be predicted
reasonably by calculating the factors FL and PL ,
ACKNOWLEDGMENTS
This study was greatly assisted by Dr, S, Yasuda,
Kisojiban Consultants Co,, Ltd, and S, Yoshida also
greatly assisted in conducting shaking table tests, The
authors wish to express their thanks to them,
Ohashi, M,, Iwasaki, T., Wakabayashi, S, and Tokida,
K. (1977), "Statistical Analysis of Strong-Motion
Acceleration Records", 9th Joint Meeting, U.S. -Japan
Panel on Wind and Seismic Effects, U.J.N.R., May,
Yasuda, S, and Tokida, K, (1980). "Soil Liquefaction
Evaluation with use of Standard Penetration Resistances", Proc., 7th World Conference on Earthquake
Engineering, Instanbul, Turkey
Iwasaki, T. and Tokida, K, (1980), "Studies on Soil
Liquefaction Observed During the Miyagi-ken Oki
Earthquake of June 12, 1978", Proc,, 7th World
Conference on Earthquake Engineering, Istanbul,
Turkey,
Kuribayashi, E. and Tatsuoka, F. (1977), "History of
Earthquake - Induced Soil Liquefaction in Japan",
Bulletin of Public Works Research Institute, Ministry
of Construction in Japan, Vol. 31,
Iwasaki, T,, Tatsuoka, F., Tokida, K, and Yasuda, S,
(1978), "A Practical Method for Assessing Soil
Liquefaction Potential Based on Case Studies at
Various Sites in Japan", 2nd International Conference
on Microzonation for Safer Construction Research and
Application, pp. 885-896,

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