chapter 5: soils and foundations exploration … · chapter 5: soils and foundations ... volume...
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439
CHAPTER 5: SOILS AND FOUNDATIONS
EXPLORATION INFORMATION ON THE LIQUEFIED FOUNDATION SOIL IN TANGSHAN AND ITS VICINITY
Zhou Shengen,1 Zhang Sumin2
Sand boils and waterspouts occurred in an extensive area in the Tangshan earthquake. The survey on the liquefaction-induced damage and the foundation soil exploration were per-formed by the Exploration Corporation of Ministry of Machine Building Industry, Academy of Railway Sciences of Ministry of Railway, No. 3 Institute of Exploration and Design of Ministry of Railway, etc., in the liquefied sites of the suburbs of Tangshan, Fengnan County, Luannan County, Laoting County and Baigezhuang village, etc., from 1977 to 1978, respec-tively.
1. Distribution of Test Sites
A total of 36 sites were investigated; all sites, excluding Baigezhuang Village, were situ-ated in the alluvial fan of the Luanhe River (see Fig. 1). Table 1 and Table 2 show the dis-tribution of test sites and the intensity in different areas, respectively.
Most of the test sites were situated at the morphological units, such as the newly depos-ited alluvial fan of the Luanhe River, the offshore alluvium of marine-continent substitution facies, the marine plain, the valley flat of the Douhe River and the first level terrace. In these areas there were relatively loose silty fine sand layers or a few moderate sand layers in the upper stratum. The water table was rather high, generally only 1-3 m below the ground sur-face.
2. Test Items and Method
Three tasks were carried out at each test site: (1) Borehole sampling for determining the physical properties of soils; (2) standard penetration tests and (3) static cone penetration tests. Generally one borehole was used to secure samples for determination of properties. Two to three holes were used for standard penetration tests. One to three holes were used for static cone penetration tests. Spacings between two neighboring boreholes were about 2 m.
1 Academy of Railway Sciences. 2 Exploration Corp., H.Q., Ministry of Machine-Building Industry
440
In the standard penetration test, slurry was used for protecting boreholes. Impact and cyclic slurry techniques were adopted for drilling. The dropping hammers used were all fal-ling automatically from the hook. In the test, it is required that settlement of the hole bottom be controlled within 5 cm. The standard penetration can fall generally to the desired depth.
Double-cylinder type static cone penetration apparatuses with an aperture of 60° were used in the static cone penetration test. A resistance-strain type probe with a wall of 70 mm in length was used. Measurement was recorded automatically, or by a YJD-1 model static strain meter, while penetration resistance was recorded at every 10 cm in depth.
3. Exploration and Test Data
Exploration and test results at each test site are given in Table 3-38 in tabular form. Sam-pling data are presented only for items related to sandy soils. Standard penetration blow counts shown in the table are average values. Blow counts over 50 blows are taken as 50 blows. In all tables, the following units are used: length (or depth) in m; water content, %; volume weight, g/cm3; particle size, mm; specific penetration resistance kg-force/cm2.
(Translator: Lu Rongjian)
Table 1. Distribution of Test Sites in Different Areas.
Area Number of test sites
With sand boils With no sand boils Total
Tangshan City 5 1 6 Fengnan County 5 3 8 Luannan County 4 3 7 Laoting County 5 2 7
Baigezhuang 4 2 6 Luan County 1 1 2
Table 2. Distribution of Test Sites in Different Intensity Areas.
Intensity Number of test sites
With sand boils With no sand boils Total
VII 0 3 3 VIII 13 4 17 IX 6 1 7 X 5 4 9
Tabl
e 3.
Exp
lora
tion
data
of B
oreh
ole
1.
(Tan
gsha
n D
ouhe
Brid
ge; a
rea
of in
tens
ity X
; wat
er ta
ble:
3.7
m; s
oil l
ique
fied;
dat
e: A
ug. 1
977.
)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Ligh
t Loa
m
3.5
4
2.5
23.6
1.
84
Fi
ne sa
nd
4.
5
9
5.
85
14
4.1
11.3
1.
68
2.
5 30
.5
59.0
8.
0
Med
ium
sand
7.
6 3
0 5.
4 19
.7
2.01
9.
0 47
.5
27.5
11
.5
4.5
9.5
50
7.3
19.9
2.
05
1.7
48.0
39
.9
8.9
1.5
Cla
yey
soil
10
.5
40
11.9
1
7 9.
9 17
.3
1.88
38.0
40
.0
16.5
5.
5
Cla
y
13
.1
16
10.2
13
.6
2.17
12.0
46
.3
29.5
12
.5
441
Tabl
e 4.
Exp
lora
tion
data
of B
oreh
ole
2.
(Wal
i, Ta
ngsh
an c
ity; a
rea
of in
tens
ity X
; wat
er ta
ble:
1.2
5 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Fi
ne sa
nd
2.
8 1
0 2.
0 26
.3
1.97
Med
ium
sand
3.8
10
2.8
21.2
2.
06
1.
5 27
62
9.
5
Silty
cla
yey
sand
Si
lty sa
nd
4.
8 1
1
C
laye
y so
il
5.8
16
6.15
2
3 3.
8 21
.0
2.04
4.2
81.0
14
.5
0.3
C
lay
6.6
33
5.6
18.8
2.
12
3.
5 15
.5
33.5
47
.5
7.15
7 6.
2 19
.1
2.04
4.5
26.5
30
.5
38.5
442
Tabl
e 5.
Exp
lora
tion
data
of B
oreh
ole
3.
(Xug
ezhu
ang,
Fen
gnan
Cou
nty;
are
a of
inte
nsity
X; w
ater
tabl
e: 1
.5 m
; soi
l unl
ique
fied;
dat
e: O
ct. 1
978)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Surf
ace
soil
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Si
lty sa
nd
2.
0 1
5 1.
7
1
6
19
54
20
Fine
sand
3.4
29
3.1
1
18
26
36
14
5
Ligh
t loa
m
4.
4 2
2 4.
1
4
27
46
16
7
Si
lt
5.
3 4
4 5.
1
1
30
52
13
4
Li
ght l
oam
6.
3 1
4 6.
0
3
11
15
45
26
Silty
sand
7.
8 5
0 7.
6
1
9
77
13
10.3
3
2 10
1
3
7
55
34
443
Tabl
e 6.
Exp
lora
tion
data
of
Bor
ehol
e 4.
(Gao
zhua
ngzi
, Fen
gan
Cou
nty;
are
a of
inte
nsity
X; w
ater
tabl
e: 1
.1 m
; soi
l unl
ique
fied;
dat
e: S
ept.
1978
)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fill
ed la
nd
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Lig
ht L
oam
F
ine
sand
3.7
27
3.5
30
48
16
6
M
ediu
m sa
nd
Fin
e sa
nd
Silt
y sa
nd
4.
8 2
7 4.
5
1
5
43
37
14
M
ediu
m sa
nd
Fin
e sa
nd
Cla
yey
soil
5.
9 5
0 5.
7
4
21
56
16
3
L
ight
loam
S
ilty
sand
7.
9 4
8 7.
5
1
13
73
13
444
Tabl
e 7.
Exp
lora
tion
data
of B
oreh
ole
5.
(Pla
nt S
eed
Ran
ch, T
angs
han
City
; are
a of
inte
nsity
X; w
ater
tabl
e: 3
.6 m
; soi
l unl
ique
fied;
dat
e: A
ug. 1
978)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Ligh
t Loa
m
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
3.
8 2
1 2.
1
2.09
4.
8 3
6 4.
0 24
.2
2.03
Si
lt sa
nd
5.
2 5
0 5.
1 20
.3
2.08
Fi
ne sa
nd
5.
8 5
0 6.
6 20
.3
2.05
M
ediu
m sa
nd
6.
3 3
8 7.
5 24
.7
2.00
2.7
4.8
65.6
26
.9
6.
9 4
4 9.
6 29
.3
1.98
4.8
14.0
32
.8
48.4
7.3
50
10.5
24
.2
2.00
3.
4 31
.8
64.8
Silty
sand
7.8
46
11.5
18
.4
2.10
1.
1 36
.5
26.0
21
.1
15.3
8.3
31
13.9
2.20
8.
8 5
0 15
.0
15.6
2.
11
0.8
3.7
29.7
45
.9
19.8
9.3
50
16.1
20
.4
2.08
M
ediu
m sa
nd
9.
8 5
0 17
.0
19.9
2.
05
2.
5 41
.5
50.4
5.
6
Ligh
t loa
m
10
.8
50
12
.7
50
14
.4
26
Fi
ne sa
nd
16
.3
50
17
.4
50
18
.3
13
C
laye
y so
il
445
Tabl
e 8.
Exp
lora
tion
data
of B
oreh
ole
6.
(Dai
futu
o, w
est o
f Tan
gsha
n; a
rea
of in
tens
ity X
; wat
er ta
ble:
1.5
m; s
oil l
ique
fied;
dat
e: A
ug. 1
977)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
C
lay
4.
65
15
3.1
1.
85
5.65
3
2 5.
0 21
.0
2.03
2.2
31.8
61
.6
4.4
Fi
ne sa
nd
6.
65
29
5.5
18.8
2.
03
5.
6 48
.2
41.0
5.
2
7.65
4
2 6.
5 14
.6
2.12
2.0
25.1
51
.0
21.9
Med
ium
sand
8.65
2
5 7.
5 25
.5`
1.96
12
.7
48.9
38
.4
32.5
Fi
ne sa
nd
9.
65
50
8.6
24.2
1.
98
7.7
38.5
53
.8
47.6
Si
lty sa
nd
10
.65
38
9.6
18.6
2.
06
15
.2
47.5
27
.4
9.9
11
.8
47
10.7
21
.3
2.04
3.
5 65
.6
29.9
24
.7
Med
ium
sand
12.6
5 5
0 11
.6
22.3
2.
02
1.
1 9.
2 56
.0
33.7
31
.9
13.6
5 2
8 12
.5
17.1
2.
08
24
.9
59.7
11
.0
4.4
Fi
ne sa
nd
14
.65
50
13.5
10
.7
2.25
8.9
41.0
34
.2
15.9
7.
8
M
ediu
m sa
nd
15
.65
50
14.7
20
.5
2.09
5.
4 75
.8
18.8
16
.8
16.6
5 5
0 15
.5
20.0
2.
08
1.
3 39
.2
48.7
10
.8
C
laye
y so
il
19.0
5
0 16
.5
19.6
2.
10
15.9
74
.6
9.5
20
.0
50
18.8
15
.5
2.17
8.6
54.7
31
.3
5.4
19
.9
19.7
2.
00
2.2
84.6
13
.2
Cla
yey
soil
Med
ium
sand
Fi
ne sa
nd
446
Tabl
e 9.
Exp
lora
tion
data
of B
oreh
ole
7.
(Dai
futu
o, w
est o
f Tan
gsha
n; a
rea
of in
tens
ity X
; wat
er ta
ble:
3.0
m; s
oil l
ique
fied;
dat
e: A
ug. 1
977)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
C
laye
y so
il
6.
3 1
2 6.
4 22
.3
2.03
72
.4
26.4
1.
2
C
laye
y so
il
7.4
28
7.3
19.5
2.
06
2.6
22.5
52
.2
21.0
1.
1
Fine
sand
8.
4 4
2 8.
3 21
.3
2.07
34
.4
55.6
10
.0
M
ediu
m sa
nd
9.3
50
9.3
12.2
2.
19
6.
5 38
.1
31.3
23
.8
16.4
Fi
ne sa
nd
10.3
1
8 11
.3
20.3
2.
09
9.
9 34
.4
41.9
13
.8
C
laye
y so
il
Fi
ne sa
nd
11
.45
48
12.2
19
.1
2.01
7.1
46.4
30
.7
15.8
12
.9
Med
ium
sand
12
.3
50
13.3
17
.0
2.10
2.7
46.0
37
.8
13.5
11
.3
13
.3
50
14.3
17
.3
2.11
1.
4 14
.9
38.2
41
.2
4.3
Si
lty sa
nd
14.3
5
0 15
.3
27.5
1.
92
4.
1 95
.9
77.0
Cla
yey
soil
16
.55
50
447
Tabl
e 10
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 8.
(Lao
bian
zhua
ng, T
angs
han;
are
a of
inte
nsity
X; w
ater
tabl
e: 3
.2 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Cul
tiv. S
oil
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
3.6
12
2.0
32.1
1.
83
Cla
y
4.65
8 4.
4 19
.6
2.05
36.7
57
.2
2.5
3.6
5.
65
3
6.2
21.1
2.
06
22
.0
72.0
5.
3 0.
7
6.65
1
1 7.
1 19
.6
2.05
1.
6 54
.0
38.7
2.
9 2.
8
7.65
1
8 8.
1 22
.4
1.90
1.
1 34
.1
53.8
9.
4 1.
6
8.64
1
6 9.
9 19
.6
1.93
0.
4 55
.5
44.0
41
.7
Med
ium
sand
9.55
1
5 10
.8
24.9
1.
88
2.0
63.5
34
.5
2.8
10.5
5
0 11
.5
22.6
2.
01
1.
0 34
.1
54.9
10
.0
11
.1
50
12.6
18
.6
2.10
2.1
21.7
63
.0
13.2
11.5
5 5
0 13
.5
19.6
2.
09
3.1
42.1
54
.8
46.6
12
.5
50
14.5
24
.9
2.10
10.1
21
.8
44.7
23
.4
19.1
Si
lty sa
nd
13
.5
50
15.5
17
.5
2.07
15
.9
57.3
26
.8
24.1
14
.5
50
17.9
16
.5
2.15
4.4
45.5
38
.0
12.1
Fine
sand
15.5
5
0 19
.5
19.1
1.
99
26
.1
64.6
8.
4 0.
9
16.5
5
0
Silty
sand
17.5
3
0
18.5
5
0
19.6
5
0
Cla
yey
soil
Fi
ne sa
nd
448
Tabl
e 11
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 9.
(Dao
di, F
engn
an C
ount
y; a
rea
of in
tens
ity X
; wat
er ta
ble:
1.1
m; s
oil u
nliq
uefie
d; d
ate:
Sep
t. 19
78)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Cla
yey
soil
4.
0 1
3 3.
8
3
69
21
7
7.0
31
6.7
14
19
47
14
6
Si
lty sa
nd
7.6
30
7.5
6
19
56
14
5
Ligh
t loa
m
8.4
27
8.2
3
9
48
29
11
Fine
sand
9.
1 4
1 9.
0
1
4
52
39
4
Silty
sand
10
.2
48
10.1
1
7
15
54
19
4
Fine
sand
11
.8
50
11.8
3
10
23
45
15
4
Si
lty sa
nd
13.9
5
0 13
.8
3
13
55
24
5
14
.6
50
14.5
2
13
57
20
8
449
Tabl
e 12
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 10
.
(Jin
gzhu
ang,
Fen
gnan
Cou
nty;
are
a of
inte
nsity
IX; w
ater
tabl
e: 1
.45
m; s
oil l
ique
fied;
dat
e: S
ept.
1978
)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Ligh
t Loa
m
3.
3
8 3.
0
1
8
58
33
Si
lty sa
nd
3.
8
8 3.
7
1
2
45
52
4.
6 8.
5 4.
4
1
47
52
5.4
5
5.1
56
44
Fine
sand
5.8
18
5.7
1
54
41
4
6.3
9
6.2
2
48
47
3
6.9
9
6.8
3
43
50
4
Med
ium
sand
7.3
13
7.2
5
52
41
2
7.8
10
7.7
16
39
41
4
8.
8
9 8.
7
15
64
18
3
Silty
sand
9.7
11
9.5
15
56
27
2
10
.9
22
10.6
8
35
50
7
450
Tabl
e 13
. Ex
plor
atio
n da
ta o
f B
oreh
ole
11.
(Fan
zhua
ng, F
engn
an C
ount
y; a
rea
of in
tens
ity IX
; wat
er ta
ble:
0.8
5 m
; soi
l liq
uefie
d; d
ate:
Sep
t. 19
78
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Fine
sand
2.3
14
2.0
1
10
75
11
3
2.
8 1
5 2.
6
3
25
58
8
6
3/
3 1
4 3.
0
1
9
81
9
Cla
yey
soil
4.3
39
4.3
1
15
76
8
5.
4 2
9 5.
2
2
12
77
9
Silty
sand
6.3
25
6.2
6
22
64
451
Tabl
e 14
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 12
.
(Xua
nzhu
ang,
Fen
gnan
Cou
nty;
are
a of
inte
nsity
IX; w
ater
tabl
e: 1
.55
m; s
oil l
ique
fied;
dat
e: S
ept.
1978
)
Type
of s
oil
Stat
ic c
one
pene
tratio
n St
anda
rd
pene
tratio
n Sa
mpl
ing
data
10
0 20
0 30
0 te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Si
lty sa
nd
2.
9
8 2.
6
2
85
8
5
3.7
5
3.4
1
65
23
11
4.
4
6 4.
2
12
80
8
5.0
10
4.7
8
84
8
5.4
6
5.1
2
93
5
Fine
sand
5.9
5
6.1
1
2
91
6
6.
3
7 6.
6
3
90
7
6.
9 1
0 7.
1
1
10
79
10
7.4
12
7.5
8
89
3
Ligh
t loa
m
7.
8
7 7.
9
1
6
80
8
5
8.
2 1
4 8.
4
8
89
3
Si
lty sa
nd
8.
7
8 8.
9
1
8
75
11
5
9.2
9
8.9
3
66
28
3
Cla
yey
soil
10
.9
16
10.6
3
13
18
44
22
Silty
sand
12.5
3
0 12
.2
2
73
25
C
laye
y so
il
12.8
1
5 12
.7
1
3
1
53
42
Silty
sand
452
Tabl
e 15
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 13
.
(Cao
gezh
uang
, Fen
gnan
Cou
nty;
are
a of
inte
nsity
IX; w
ater
tabl
e: 1
.05
m; s
oil l
ique
fied;
dat
e: S
ept.
1978
)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Cla
yey
soil
2.
5 1
0 2.
3
1
10
48
19
22
Si
lty sa
nd
4.
3 1
9 4.
1
1
6
74
15
4
5.
3 1
6 5.
0
7
22
57
11
3
Fi
ne sa
nd
5.9
9
5.7
12
36
45
7
Silty
sand
6.3
27
6.0
5
40
49
6
7.
4 2
1 7.
1
4
48
45
3
Li
ght l
oam
7.
8 2
7 7.
5
1
5
54
37
3
Fi
ne sa
nd
9.
3 2
9 9.
0
2
21
65
8
4
9.
8 2
9 9.
5
2
70
21
7
453
Tabl
e 16
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 14
.
(Yan
jiazh
uang
, Fen
gnan
Cou
nty;
are
a of
inte
nsity
IX; w
ater
tabl
e: 1
.25
m; s
oil l
ique
fied;
dat
e: S
ept.
1978
)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Silty
fine
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 0.
1-0.
05
<0.0
5
sand
1.8
14
1.5
17
77
6
M
ediu
m sa
nd
2.8
15
2.5
8
51
39
2
Fine
sand
3.
8 2
3 3.
5
11
59
27
3
Silty
sand
4.
8 2
3 4.
5
1
24
71
4
Si
lty li
ght
loam
5.8
30
5.5
4
22
49
21
4
Silty
sand
6.
8 1
0 6.
5
1
46
53
Cla
yey
soil
Fi
ne sa
nd
454
Tabl
e 17
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 15
.
(Xie
zhua
ng, L
uan
Feng
nan
Cou
nty;
are
a of
inte
nsity
IX
; wat
er ta
ble:
1.0
m; s
oil l
ique
fied;
dat
e: A
pr. 1
977
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fine
sand
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
M
ediu
m sa
nd
2.
3 1
1 2.
7 18
.0
1.94
1.
8 45
.5
42.5
9.
2 1.
0
3.25
1
5 3.
4 22
.7
2.01
0.7
7.7
62.2
29
.4
27.9
Si
lty sa
nd
4.
3 2
4 4.
3 23
.5
1.89
16
.8
65.8
17
.4
14.5
5.
25
23
5.3
22.8
2.
07
9.5
60.9
29
.6
24.2
Fi
ne sa
nd
6.
25
26
6.3
19.3
2.
08
2.
8 36
.7
47.1
13
.4
11.1
7.
20
43
7.4
20.4
2.
05
2.
1 46
.2
48.2
3.
5
Med
ium
sand
8.2
50
8.2
18.5
2.
06
3.
6 41
.2
50.2
5.
0
Fine
sand
9.3
50
9.3
21.1
2.
07
4.
4 46
.9
43.2
5.
5
Med
ium
sand
10.3
5
0 10
.3
17.8
1.
94
15
.8
54.5
24
.5
5.2
Fi
ne sa
nd
11
.3
50
11.3
16
.7
2.09
10.6
32
.7
49.5
7.
2
12.3
5
0 12
.2
12.9
2.
04
3.5
28.1
39
.0
23.0
6.
4
Silty
sand
13.3
5
0 13
.1
21.4
2.
05
0.
5 36
.3
54.5
8.
7
14.3
4
6 14
.3
20.2
2.
04
0.
5 10
.5
60.9
28
.1
19.2
C
laye
y so
il
15.3
5
0 15
.4
23.4
2.
00
0.
5 1.
5 36
.5
61.5
55
.4
16.4
19
.2
2.00
Fi
ne sa
nd
18
.3
50
18.1
19
.6
2.06
0.1
2.4
76.7
20
.8
14.1
C
laye
y so
il
455
Tabl
e 18
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 16
.
(Eas
t Tuo
zito
u, L
uan
Cou
nty;
are
a of
inte
nsity
IX
; wat
er ta
ble:
3.5
m;
soil
unliq
uefie
d; d
ate:
Apr
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fine
sand
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
Ligh
t Loa
m
1.
2 1
4 2.
1 11
.3
2.10
15.5
38
.5
33.0
13
.0
2.
25
22
3.0
19.8
1.
96
0.
1 10
.0
60.0
29
.9
25.9
M
ediu
m sa
nd
3.
25
23
4.1
19.6
2.
13
2.
4 24
.8
48.9
23
.9
22.1
4.
25
31
7.6
14.2
2.
17
0.4
10.2
31
.4
38.8
19
.2
15.6
5.
45
10
8.2
14.6
2.
09
5.
4 32
.4
45.2
17
.0
14.5
Si
lty sa
nd
6.
3
7 9.
1 19
.7
2.05
0.5
36.0
47
.5
16.0
12
.8
7.35
3
2 12
.1
14.7
2.
12
17
.2
47.0
27
.7
8.1
8.
35
31
13.0
15
.7
2.16
13.5
45
.8
31.7
9.
0
Cla
yey
soil
9.
3 5
0
10.3
8
Fine
sand
12.3
4
6
Cla
yey
soil
13
.3
50
M
ediu
m so
il
14.3
1
0
Cla
yey
soil
15
.3
35
Fi
ne sa
nd
16
.3
50
17
.4
50
456
Tabl
e 19
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 17
.
(Zhu
angl
izhu
ang,
Lua
n C
ount
y; a
rea
of in
tens
ity V
III ;
wat
er ta
ble:
2.8
m; s
oil u
nliq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cul
tiv. s
oil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Cla
yey
soil
2.3
4
2.2
18.4
1.
89
13.0
34
.5
52.5
42
.3
Fine
sand
3.3
16
3.2
13.8
2.
13
7.
2 41
.8
23.4
18
.6
17.3
4.
3 2
2 4.
1 18
.3
2.10
3.6
28.2
57
.4
10.8
Silty
sand
5.3
23
5.1
21.9
1.
99
0.8
74.1
25
.1
24.2
6.
3 5
0 6.
1 20
.4
2.09
10
.5
67.4
22
.1
21.1
Fi
ne sa
nd
7.
25
41
7.1
20.0
2.
09
15
.1
73.8
8.
0 3.
1
8.3
49
8.1
23.2
2.
02
0.6
35.4
64
.0
40.0
M
ediu
m sa
nd
9.
3
2 11
.1
21.4
2.
01
0.8
63.2
36
.0
30.1
10
.3
4
13.0
23
.6
1.96
1.
5 68
.5
30.0
28
.3
Silty
sand
11.3
1
4
12.3
5
0
Cla
yey
soil
13
.3
47
14
.3
3
Si
lty sa
nd
17
.3
13
Cla
yey
soil
457
Tabl
e 20
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 18
.
(Wan
ggua
nzha
i, Lu
anna
n C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
3.6
m; s
oil l
ique
fied;
dat
e: A
ug. 1
977)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Ligh
t loa
m
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Silty
sand
1.
3 1
2 1.
1 11
.5
1.79
1.0
17.0
51
.4
30.6
27
.5
Med
ium
sand
2.3
20
2.1
6.1
1.77
4.8
59.5
33
.0
2.7
3.
3 1
2 3.
1 15
.7
1.99
6.5
44.7
40
.2
8.6
C
laye
y so
il
4.3
15
4.0
32.8
1.
81
5.3
20
5.1
16.1
2.
10
10
.1
25.0
38
.7
26.2
15
.4
Fine
sand
6.3
23
6.1
16.0
2.
10
8.
0 33
.0
44.0
15
.0
12.8
7.
3 1
1 7.
0 21
.4
2.04
Li
ght l
oam
9.3
3
8.0
26.8
1.
95
10.3
1
5 10
.1
20.9
2.
00
2.
0 18
.4
62.6
7.
0 12
.6
Fine
sand
11.3
4
2 11
.1
21.8
2.
03
32.1
60
.2
7.7
12
.3
48
12.1
18
.9
2.01
13.2
43
.0
34.7
9.
1
Med
ium
sand
13.3
5
0 13
.1
22.7
2.
00
51
.7
45.9
2.
8
14
.3
46
14.0
20
.9
2.02
3.6
67.4
29
.0
26.2
Silty
sand
15.3
2
7 15
.0
10
.1
67.3
22
.6
458
Tabl
e 21
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 19
.
(Jia
npao
, Lua
nnan
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 1
.1 m
; soi
l liq
uefie
d; d
ate:
ug.
197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cul
tiv. s
oil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Fine
sand
1.3
6
1.2
25.1
1.
82
28.5
68
.3
3.0
2.3
5
2.2
24.7
1.
85
3.
0 64
.3
31.2
1.
5
Med
ium
sand
3.
3
6 3.
1 25
.4
1.89
1.9
70.0
27
.1
1.0
Fine
sand
4.3
7
4.1
26.3
1.
93
20.6
73
.0
6.4
Med
ium
sand
5.3
6
5.2
30.0
1.
89
23.6
51
.8
24.6
20
.3
with
a sm
all
amou
nt o
f
6.3
14
6.0
37.1
60
.5
2.4
gr
avel
7.
3 1
1 7.
2 23
.2
1.98
3.6
72.5
21
.6
2.3
C
laye
y so
il
8.
3 1
9 8.
0
7.
5 12
.9
52.8
19
.4
7.4
9.3
24
9.0
22.7
2.
01
3.7
21.4
59
.4
14.0
1.
5
459
Tabl
e 2
2. E
xplo
ratio
n da
ta o
f Bor
ehol
e 20
.
(Gao
caoz
huan
g, L
uann
an C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
1.1
m; s
oil u
nliq
uefie
d; d
ate:
Aug
. 19
77)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cul
tiv. s
oil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Fi
ne sa
nd
Cla
yey
soil
1.
3 1
5
with
silty
2.3
23
2.1
17.8
2.
03
0.
9 26
.5
53.5
19
.1
17.2
sa
nd in
terc
a-
3.
3 1
0 4.
1 18
.6
2.09
3.1
29.0
52
.9
15.0
13
.7
latio
n
4.3
35
5.1
18.8
2.
07
2.07
36.0
56
.3
7.7
Fi
ne sa
nd
5.
3 2
1 6.
1 20
.7
2.12
1.
7 20
.8
77.5
58
.1
6.3
30
Si
lty sa
nd
7.
3
3
8.3
1
C
laye
y so
il
9.3
21
10
.3
50
Si
lty a
nd fi
ne
11
.3
25
sa
nd in
terc
al.
12
.3
28
13
.3
50
C
laye
y so
il
14.3
3
460
Tabl
e 23
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 21
.
(Cre
mat
oriv
um, L
uann
an C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
3.1
m; s
oil u
nliq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Silty
sand
3.
3 1
9 2.
1 13
.4
4.7
24.8
43
.5
27.0
17
.1
4.3
15
3.1
17.6
1.
89
2.
8 52
.7
38.7
5.
8
Med
ium
sand
5.3
20
4.1
19.1
2.
06
0.
4 49
.6
43.4
6.
6
6.3
14
5.1
16.4
2.
08
8.4
46.9
44
.7
36.3
Si
lty sa
nd
8.
3
3 6.
1 22
.0
2.01
0.
6 36
.0
63.4
52
.6
9.3
16
8.1
20.2
2.
08
Cla
yey
soil
10
.3
11
10.1
16
.5
2.15
an
d si
lty sa
nd
11
.3
42
11.1
18
.8
2.03
7.1
31.2
45
.5
16.2
12
.8
inte
rcal
atio
n
12.3
5
0 12
.1
16.6
2.
11
13
.1
42.3
35
.4
9.2
13
.3
8
C
laye
y so
il
Fine
sand
Cla
yey
soil
461
Tabl
e 24
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 22
.
(Xin
zhua
ngzh
i, Lu
anna
n C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
0.8
m; s
oil
lique
fied;
dat
e: A
ug. 1
977)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Sand
y cl
ay
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
>10
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
Fine
sand
1.
3
8 1.
1 26
.0
1.93
26.4
63
.2
10.4
2.
3
7 2.
1 29
.0
1.86
C
laye
y sa
nd
3.
3
4 4.
1 27
.9
1.93
11.0
83
.5
5.5
4.3
18
5.1
27.5
1.
90
8.
7 84
.3
7.0
5.3
22
7.1
29.7
1.
86
8.
8 84
.4
6.8
Fine
sand
6.3
28
8.1
20.6
1.
99
3.
5 52
.0
43.5
0.
8 0.
2
7.
3 2
4 9.
1 24
.4
1.93
13
.5
72.9
10
.8
2.8
8.3
19
10.1
24
.2
1.98
3.
5 3.
4 8.
4 70
.0
13.1
1.
6
C
oars
e an
d
9.3
22
11.0
16
.3
69.0
13
.1
1.6
10.3
1
7
12.3
7
Med
ium
sand
13.3
1
1
14.3
2
8
Ligh
t loa
m
462
Tabl
e 25
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 23
.
(Wei
gezh
uang
, Lua
nnan
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 1
.35
m; s
oil
lique
fied;
dat
e: A
ug. 1
977)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Fi
ne sa
nd
1.
3 1
0 1.
1 27
.2
1.84
0.
8 91
.7
7.5
2.
3 1
1 2.
1 27
.8
1.91
5.
1 84
.5
10.4
Cla
yey
soil
3.
3
1 3.
1 38
.7
1.87
4.
3
1 4.
1 30
.5
1.89
0.
3 79
.5
20.2
15
.8
5.3
13
5.1
26.4
1.
92
81
.8
18.2
17
.0
6.3
23
6.1
24.2
1.
97
45.9
51
.8
2.3
Fi
ne sa
nd
7.
3 2
2 7.
1 24
.7
1.95
49
.8
46.5
3.
7
8.3
13
8.1
26.0
1.
96
29.6
66
.1
4.3
9.
3 2
4 9.
1 21
.7
1.97
14.2
70
.8
14.0
1.
0
10.3
1
8 10
.1
24.1
1.
97
3.
4 60
.7
31.5
4.
4
Med
ium
sand
11.3
1
6
12.3
7
13.3
7
Cla
yey
soil
14
.3
13
15
.3
15
16
.3
11
17
.3
9
463
Tabl
e 26
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 24
.
(Bai
gezh
uang
Ran
ch, B
ranc
h N
o. 6
; are
a of
inte
nsity
VII
I; w
ater
tabl
e: 1
.0 m
; soi
l liq
uefie
d; d
ate:
Oct
. 197
8)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 0.
1-0.
05
<0.0
5
Silty
sand
2.0
15
2.6
10
79
11
Si
lty c
laye
y
2.9
8
5.5
35
59
6
so
il
5.
8 2
1 7.
0
50
44
6
Silty
sand
7.
3 2
4 12
.2
2
85
13
Si
lty c
laye
y
so
il
8.3
7
Silty
sand
9.8
31
Silty
cla
yey
11
.2
7
so
il
Si
lty sa
nd
12
.5
37
Si
lty c
laye
y
so
il
14.9
9
464
Tabl
e 27
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 25
.
(Bai
gezh
uang
Ran
ch, B
ranc
h N
o. 1
1; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
0.6
5 m
; soi
l liq
uefie
d; d
ate:
Oct
. 197
8)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 0.
1-0.
05
<0.0
5
Cla
yey
soil
8.
45
11
8.3
5
44
40
11
Silt
9.7
14
9.4
4
56
40
Si
lty sa
nd
10
.2
24
10.9
6
81
13
Silty
sand
C
laye
y so
il
465
Tabl
e 28
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 26
.
(Bai
gezh
uang
Ran
ch, B
ranc
h N
o. 4
; are
a of
inte
nsity
VII
; wat
er ta
ble:
0.7
5 m
; soi
l liq
uefie
d; d
ate:
Oct
. 197
8)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Si
lty li
ght
4.
8 1
0 4.
5
73
27
lo
am
5.7
9
5.4
75
25
Silty
sand
6.
3 1
5 6.
0
7
86
7
Si
lty sa
nd
6.7
19
6.4
6
89
5
Silty
sand
7.
8 2
6 7.
0
31
60
9
Fine
sand
8.
2 3
0 7.
5
51
43
6
Silty
sand
9.
4 1
1 9.
1
50
42
8
Ligh
t loa
m
9.7
17
9.5
75
19
6
Si
lty sa
nd
10.7
2
3 10
.4
61
32
7
C
laye
y so
il
Si
lty sa
nd
12
.7
19
12.4
56
38
6
466
Tabl
e 29
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 27
.
(Che
mic
al F
ertil
izer
Pla
nt, B
aige
zhua
ng R
anch
, are
a of
inte
nsity
VII
I; w
ater
tabl
e: 0
.65
m; s
oil l
ique
fied;
dat
e: O
ct. 1
978)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Silty
cla
yey
5.
3 1
1 5.
0
31
61
8
soil
6.3
5
6.0
3
71
26
Silty
fine
7.3
20
7.0
72
23
5
sa
nd
8.3
14
8.0
1
44
50
5
9.
3 1
6 9.
0
1
66
29
4
C
laye
y so
il
10
.8
14
10.5
3
74
20
3
Silty
sand
12.3
1
8 12
.0
3
72
15
10
467
Tabl
e 30
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 28
.
(Bai
gezh
uang
Ran
ch, B
ranc
h N
o. 3
; are
a of
inte
nsity
VII
; wat
er ta
ble:
0.6
5 m
; soi
l unl
ique
fied;
dat
e: O
ct. 1
978)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Cla
yey
soil
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
11.1
1
5 10
.8
11
67
22
Silt
12.8
4
3 12
.5
1
39
52
8
Li
ght l
oam
13.8
5
0 13
.5
29
64
7
Silty
sand
14.4
1
6 14
.1
2
47
42
9
Si
lty c
laye
y
15.2
2
5 14
.9
1
13
54
23
9
soil
15.8
5
0 15
.5
8
54
33
5
Ligh
t loa
m
Silty
sand
Silty
sand
468
Tabl
e 31
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 29
.
(Bai
gezh
uang
Ran
ch, B
ranc
h N
o. 1
; are
a of
inte
nsity
VII
; wat
er ta
ble:
1.0
m; s
oil u
nliq
uefie
d; d
ate:
Oct
. 197
8)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Fille
d la
nd
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
0.1-
0.05
<0
.05
Silty
cla
yey
soil
4.8
14
4.5
73
23
4
Silty
sand
5.
8 2
4 5.
6
38
54
8
Silty
cla
yey
6.
8 2
5 6.
5
82
15
3
soil
Si
lty fi
ne
8.
3 24
` 8.
0
2
53
40
5
sa
nd
Si
lty sa
nd
469
Tabl
e 32
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 30
.
(Mag
ezhu
ang,
Lao
ting
Cou
nty;
are
a of
inte
nsity
VII
; wat
er ta
ble:
2.5
m; s
oil u
nliq
uefie
d; d
ate:
Aug
.. 19
77)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
C
laye
y so
il
2.
3
3
4.3
9
Fi
ne sa
nd
5.
3 1
7 4.
0
1.94
36
.7
60.4
2.
9
with
inte
r-
6.
3 1
7 5.
0
1.91
0.2
61.6
35
.8
2.4
ca
latio
n
7.3
21
6.0
1.
92
0.
5 64
.9
33.6
1.
0
8.3
15
7.0
1.
89
33.0
64
.5
2.5
9.
3 2
2 8.
0
1.1
65.5
30
.5
2.9
M
ediu
m sa
nd
10
.3
23
9.0
1.
97
7.
2 43
.8
41.7
7.
3
11.3
3
2 10
1.86
2.2
66.7
28
.7
2.4
M
ediu
m sa
nd
12
.3
37
11.0
1.91
87
.5
12.0
0.
5
Ligh
t loa
m
13
.3
30
12.4
14.9
75
.8
8.5
0.8
w
ith in
ter-
14.3
18
13
.0
7.4
29.4
49
.2
11.2
2.
8
cala
tion
of
15
.3
50
16.0
48.5
51
.5
37.0
si
lty sa
nd
16
.3
50
18.0
10
.6
59.6
29
.8
14.9
17
.3
28
Fi
ne sa
nd
18
.3
31
470
Tabl
e 33
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 31
.
(Lon
gwan
gmia
o, L
aotin
g C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
2.2
5 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Sand
y cl
ay
D
epth
#
of
blow
Sa
mpl
ing
dept
h W
ater
co
nten
t V
ol.
wt.
10–2
2-
0.5
0.5-
0.25
0.
25-
0.1
<0.1
0.
1-0.
05
Si
lty sa
nd
2.
3
4 2.
0 22
.7
1.80
13
.8
69.5
16
.7
10.8
3.
3
5 3.
2 35
.0
1.80
4.
3
0 4.
2 30
.6
2.05
Si
lty c
laye
y
5.3
2
6.1
41.5
1.
87
soil
6.
3
3 7.
1 29
.3
1.92
0.
1 58
.9
41.0
36
.6
7.3
3
8.1
24.6
1.
98
10.4
79
.8
9.8
8.
3 2
5 9.
1 27
.3
1.96
6.
5 87
.0
6.5
9.
3 2
4 10
.1
23.6
1.
96
1.
0 25
.8
69.3
3.
9
Silty
sand
10.3
2
4 11
.0
10
.5
38.4
43
.5
7.6
1.9
11..3
2
5 12
.0
6.9
65.6
27
.5
5.5
Fine
sand
12.3
3
5
13.3
3
0
Gra
vel s
and
14
.3
35
15
.3
18
C
laye
y so
il
471
Tabl
e 34
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 32
.
(Cai
gezh
uang
, Lao
ting
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 2
.3 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
C
laye
y so
il
3.
3 1
4 2.
1 30
.6
1.99
1.
7 63
.2
35.1
26
.0
4.3
20
3.1
29.5
1.
89
52.4
45
.4
2.2
5.
3 1
0 4.
1 26
.3
1.95
38
.4
59.7
1.
9
6.3
15
5.2
25.2
1.
96
51.0
47
.1
1.9
7.
3 1
6 6.
1 26
.4
1.97
0.2
71.5
27
.1
1.2
8.
3 1
5 7.
1 28
.7
1.93
1.7
62.0
35
.4
0.9
M
ediu
m sa
nd
9.
3 4
5 8.
2 27
.9
1.93
59.5
39
.3
1.2
10.3
3
6 9.
1 24
.0
2.00
62
.0
37.1
0.
9
11.3
3
1 10
.1
23.9
1.
96
1.
0 64
.4
33.6
1.
0
12.3
2
3 11
.1
26.3
2.
0
1.6
68.9
29
.1
0.4
C
laye
y so
il
13.3
3
2 12
.1
26.5
1.
94
0.
4 58
.0
40.4
1.
2
14.3
2
4 17
.2
0.6
88.8
10
.6
Fi
ne sa
nd
15
.3
25
18.2
4.5
50.9
36
.8
7.8
17
.3
50
19.2
2.
9 26
.5
44.2
21
.2
5.2
M
ediu
m sa
nd
18
.3
50
19
.3
50
472
Tabl
e 35
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 33
.
(Liu
bian
zhua
ng, L
aotin
g C
ount
y; a
rea
of in
tens
ity V
III;
wat
er ta
ble:
2.3
m; s
oil l
ique
fied;
dat
e: A
ug. 1
977)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
C
laye
y so
il
3.
3
9 2.
1 32
.6
1.89
4.
3
2 3.
1 30
.6
1.89
1.
3 80
.5
18.2
Fine
sand
5.3
15
4.3
32.6
1.
87
0.6
25.0
74
.4
C
laye
y so
il
6.3
20
5.2
25.2
1.
93
1.
1 66
.5
31.7
0.
7
with
an
7.
3 2
7 6.
1 24
.1
2.01
1.0
79.0
19
.5
0.5
in
terc
alat
ion
8.
3 1
5 7.
1 19
.7
2.04
4.
8 15
.3
65.7
12
.2
2.0
of
fine
sand
9.3
17
8.1
11
.7
46.8
36
.7
4.8
10
.3
16
9.1
23.3
2.
5 46
.7
46.7
4.
1
11.3
1
7 10
.2
22.5
7.2
18.5
57
.7
11.2
5.
5
12.3
2
0 11
.0
18
.2
61.3
16
.1
4.4
M
ediu
m sa
nd
13
.3
23
12.0
15.8
56
.2
22.0
5.
5
14.3
2
0
C
laye
y so
il
473
Tabl
e 36
Exp
lora
tion
data
of B
oreh
ole
34.
( Cot
ton
oil p
lant
, Lao
ting
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 2
.5 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
C
lay
2.3
4
1.0
1.
78
3.3
1
2.4
29.2
1.
95
2.1
72.6
25
.3
21.4
Si
lty sa
nd
4.
3
0 6.
0
1.84
5.
3
1 8.
1 22
.3
2.02
4.3
69.7
24
.9
1.1
6.
3
3 9.
1 21
.0
2.00
6.
6 27
.6
55.4
10
.0
0.4
Si
lty c
laye
y
7.3
1
10.1
21
.4
1.96
8.
0 19
.7
66.5
5.
0 0.
8
soil
8.
3 2
1 11
.1
25.5
1.
96
4.
9 61
.6
32.6
0.
9
9.3
31
12.1
23
.2
2.02
5.6
79.4
14
.8
0.2
10
.3
36
13.1
18
.4
2.11
41
.0
22.5
32
.5
3.5
0.5
M
ediu
m sa
nd
11
.3
30
15.0
25.2
74
.5
12
.3
28
17.0
24
.4
45.6
30
.0
13.2
G
rave
l san
d
13.3
1
8 18
.0
0.
1 12
.6
73.8
13
.5
15
.3
30
20.0
2.2
52.1
42
.5
3.2
Li
ght l
oam
16.3
9
Silty
sand
17.3
4
1
Fine
sand
18.3
4
9
Med
ium
sand
20.3
5
0
474
Tabl
e 37
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 35
.
(Upp
er Y
uzhu
ang,
Lao
ting
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 2
.9 m
; soi
l liq
uefie
d; d
ate:
Aug
. 197
7)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
Cla
yey
soil
2.
35
0
1.5
29.1
1.
87
5.3
4
5.0
29.3
1.
84
0.1
35.9
64
.0
Fi
ne sa
nd
6.
3 1
4 6.
0 27
.2
1.91
17
.0
54.6
28
.4
19.9
7.
3 1
9 7.
0 26
.2
1.86
0.7
32.1
57
.9
9.3
8.
3 1
7 8.
1 23
.8
1.88
0.2
29.8
67
.5
2.5
Fi
ne sa
nd
9.
3 1
7 9.
2 21
.1
1.88
4.
7 0.
5 87
.9
66.6
0.
3
10.3
1
7 10
.0
27.2
1.
2 63
.2
34.2
1.
4
11.3
2
0 11
.0
26.4
1.
90
59
.5
38.5
1.
6 0.
4
12.3
1
3 12
.3
30.5
1.
91
2.2
55.0
41
.9
0.9
13.3
1
5 13
.4
19.4
1.
97
5.8
36.1
44
.7
11.0
2.
4
Coa
rse
sand
14.3
1
1 16
.0
19.9
2.
01
15.3
2
0 18
.0
15.4
2.
10
31.6
51
.2
17.2
10
.5
16.3
7 19
.0
18.1
2.
03
21.8
54
.4
23.8
13
.2
Cla
yey
soil
17
.3
12
20
15.3
2.
11
19.0
50
.9
30.1
13
.3
18.3
3
5
19.3
2
6
20.3
5
0
475
Tabl
e 38
. Ex
plor
atio
n da
ta o
f Bor
ehol
e 36
.
(Mao
zhua
ng C
omm
une,
Lao
ting
Cou
nty;
are
a of
inte
nsity
VII
I; w
ater
tabl
e: 2
.3 m
; soi
l unl
ique
fied;
dat
e: A
ug. 1
977)
Type
of
Stat
ic c
one
Stan
dard
pe
netra
tion
Sam
plin
g da
ta
soil
pene
tratio
n te
st
Pa
rticl
e an
alys
is
Dep
th
# of
bl
ow
Sam
plin
g de
pth
Wat
er
cont
ent
Vol
. w
t. 10
–2
2-0.
5 0.
5-0.
25
0.25
-0.
1 <0
.1
0.1-
0.05
3.3
1
2.0
1.
81
Cla
yey
soil
4.
3 1
4 4.
1 26
.0
2.00
0.1
19.6
78
.0
2.3
5.
3
9 5.
1 28
.6
1.91
33
.7
60.7
5.
6
6.3
11
6.1
28.8
1.
93
0.
1 47
.6
49.5
2.
8
7.3
10
7.1
26.0
1.
82
0.
4 40
.5
57.0
2.
1
Fine
sand
8.3
21
8.1
27.4
1.
89
0.
5 61
.6
36.5
1.
4
9.3
19
9.0
23
.1
38.4
32
.5
6.0
1
M
ediu
m sa
nd
10
.3
18
10
16
.8
33.6
43
.2
6.4
11
.3
23
12.0
2.
9 60
.5
28.1
8.
5
12
.3
18
13.0
4.
9 16
.2
40.7
36
.0
2.2
C
laye
y so
il
13.3
2
8 14
.0
13
.8
47.7
31
.4
7.1
w
ith a
thin
14.3
4
5
inte
rcal
atio
n
15.3
7
of si
lty sa
nd
Fi
ne sa
nd
476
477
Figure 1. Distribution of test locations.
478
SAND LIQUEFACTION AT LUJIATUO MINE
Wang Buyun*
Lujiatuo Mine is situated about 20 km northeast of Tangshan at the first level terrace on the west bank of the Shahe River. Its geographic position is shown in Figure 1. The surface elevation was 28-29m (before the 1976 quake). The site is about 500 m wide in the north-south direction and 1100 m in the east-west direction as shown in Figure 2. The site is located in the area of intensity IX in the Tangshan earthquake.
The foundation soil at the Lujiatuo Mine was mainly composed of saturated fine sand layers which were liquefied to some extent in the Tangshan earthquake. To investigate the seismic effect on saturated foundation sandy soil, standard penetration tests, static cone penetration tests and other geotechnical tests were performed along with earthquake damage surveys after the earthquake. Results are compared with the exploration data prior to the quake.
1. Macro-Investigation of Sand Liquefaction
(1) Water spouts and sand boils. Water spouts and sand boils in the eastern and western parts of the working site were more extensive than in the central part. Sand boils in the western part were distributed in a leaf-shaped pattern, and the diameter of sand boils was generally 2-4 m with a spouting water column as high as 400 mm during the quake. In the eastern area, the sand boils were generally distributed in a pattern of circular dots like a series of pearls with diameters about 1-2 m; slightly smaller than those in the western part. Most sands brought to the ground surface in the sand spouting were light yellow in color, fine grained and uniformly distributed. The gradation of the sand taken from the sand boils is summarized in Table 1. The particle composition of the undisturbed sand in the vicinity of E-1 and E-2 pump houses is listed in Table 2. By comparison, the gradation of the spouted sand is similar to that of the undisturbed sand above the depth of 5.40 m and is different from that below 7.71 m in depth (Figure 11).
Water spouts and sand boils not only occurred outdoors but indoors as well. In the boiler house east of the site, the ground heaved and cracked, and its surface was submerged in water from the liquefied sand. Water spouts also occurred in the basement of a winch workshop of the main shaft in the west, and a total of about 1 m3 of sand was brought to surface. Differential settlement of the workshop resulting from the sand boils reached 90 mm high and 60 mm wide. This caused the reinforced concrete foundation of the winch workshop to fracture (Figure 3).
* Shanxi Design Institute of Coal Mine
479
(2) Uneven heaving in buildings. The peat precipitation tanks were located on the east side of the site (Figure 2). There were four main tanks, Nos. 1 to 4 from west to east. Tanks are 4 m in width and height. The length of No. 1 and No. 4 tanks was 143.45 m and that of No. 2 and No. 3, 146 m. Adjacent to the main tank to the south were secondary tanks. The total storage capacity of the tanks was 108,000 m3 (Figure 4). During the quake, all tanks were full of peat water. A 40 m wide, 10-ton crane was parked on top of the reinforced con-crete rail wall about 30 m from the west end of the No. 3 tank (Figure 5). The ground, rail wall and tanks cracked in the quake, causing serious leakage of peat water from the tanks. In fact, the peat water was completely drained in just 5 hours after the quake. The wall near the No. 3 and No. 4 tanks experienced large horizontal displacements and differential settle-ments. The damage survey conducted in October, 1976 indicated a large relative horizontal displacement of the north wall of 268 mm, the south wall 150 mm, a vertical settlement of 93 mm for the north rail wall, and 139 mm for the south rail wall (Figure 6). Moreover, a lon-gitudinal crack went through the No. 3 and No. 4 tanks near the tank bottom along the edge of the tank foundation. The crack was 5-40 mm wide, about 200 m long, and offset of the fissure was 10-40 mm with sand from sand boils found in the crack. Transverse cracks, 5-10 m in length also occurred parallel to the longitudinal crack. Serious depression occurred locally on the bottom of the tank, and two large pits due to the depression were found. The largest pit was located across the south-east corner of the No. 4 tank and the north-east corner of the secondary tank. The area of depression was about 150m2 (Figure 7). Liquefaction-induced fracture and offset were also found in both pipelines buried at 3 m depth and observation wells at the south side of the No. 3 and No. 4 tanks (buried depth of which was over 3 m).
A boiler house is located in the south-central area of precipitation tanks. The building covered an area of only 5.7 m ×7.0 m. The west wall of the building was placed directly on an existing curtain wall; the foundation was rather shallow. Due to liquefaction of the foun-dation soil, the entire building tilted to the west nearly 20°.
The foundation of a pump house, west of the boiler house, was 9 m deep. Although sand boils occurred in the vicinity of the building, no building damage or tilting was found. The drying plant of the floatation processing plant was 7 stories high with a total height of 32.5 m. Below the height of 17.75 m was a four-story cast-in-place reinforced concrete framed structure with a reinforced concrete raft foundation. Above the height of 17.75 m were steel beams and columns, R.C. cast-in-place slab and steel roof trusses with precast corrugated roof slabs. The foundation sandy soils liquefied during the earthquake and a few sand boils were observed in the neighborhood of the plant. After the quake, the cinder block wall above the height of 17.75 m experienced cracks, and the roof top displaced 50 mm.
(3) Ground deformation. The whole ground surface at the site settled. Because all bench marks in the mining district were destroyed, settlements were difficult to measure. Based on the measured relative settlement of the building, the average settlement of the ground at the site was estimated at up to 30 cm. In addition, there were some depressions, 10-20 m in diameter, in the southeast and central parts of the site. The greatest depression exceeded 1 m in depth. This could be caused by the collapse of some small coal mine shafts.
480
(4) Cracking of the shaft. Circular cracks of different severity occurred on the walls of all vertical shafts located in the area with soil liquefaction. The inner diameter of the secondary shaft was 5.6 m and the thickness of the upper shaft wall was 500 mm. A circular crack occurred at 13.6 m from shaft entrance. The shaft wall fractured and dislocated up to 130 mm in the southeast direction. Cracks developed along a height of 1 m from the entrance (Figure 8). Sand was observed to continue to flow out of the cracks with the total amount estimated at 1 m3 on November 15, 1976.
Moreover, the mine shaft of the Xujialou Mine and the Qianjiaying Mine cracked simi-larly. The vertical shaft of the Xujialou Mine dislocated laterally 30-110 mm at a depth of 5.05-13.23 m; sand-water mixture was found to blow out of the cracks. The shaft tower of the vertical shaft, 49.50 m high, inclined to the west and south by 335 mm and 145 mm, respectively. Elevating center line at the entrance of the shaft displaced 249-288 mm to the west and 80-120 mm to the south. The average settlement of the shaft was 200 mm. Many cracks occurred on the walls of the R.C. box foundation (Figure 9). Some cracks were observed to concentrate at the girder support of the wall at the east and west sides from the bottom slab to the top; some cracks occurred on the foundation beam from the top of the beam to the bottom slab. The sleeve of the bore hole in the Dongfeng shaft of the Qianjiaying Mine tilted northwestward from 10 m above, and displaced 400 mm on the sur-face.
2. Exploration of the Liquefied Sandy Soils
The subsurface exploration did not indicate significant lateral variation of the foundation soils at the Lujiatuo Mine (Figure 10). The boring log in Figure 11 shows shallow layers of the Quaternary system.
(1) Standard Penetration Test (SPT). Winch, automatic off-hook and free falling tech-niques were used in the standard penetration test. Due to significant difference in blow counts obtained in the standard penetration tests by use of rotating boring and impact boring techniques, with the impact boring giving smaller blow counts (Figure 12), the rotating boring was used and the borehole was filled with slurry.
Blow counts are quite scattered. Blow counts of soils at the same depth but from the borehole only a few meters apart can be quite different. To obtain accurate test results, 10 SPT tests were conducted at the depth interval of 1 meter in an area. For statistical analysis, the maximum or minimum values were deleted (not exceeding 10%). Then, the average value was calculated.
Figure 13 and Table 3 show the comparison of SPT results before and after the quake. The data indicate that the blow counts of saturated fine and medium sands located at 5.4 meters below the ground surface are 1 to 5 blows less after the quake than before. The blow counts of the sand layer at the depth of 4.0 to 5.4 meters decrease greatly after the quake. It must be pointed out that these tests were carried out 9 months after the quake.
(2) Static cone penetration test (SCPT). Static cone penetration tests were carried out to identify the liquefaction of saturated sandy soils in the Lujiatuo Mine. A hydraulic double
481
cylinder cone was used. The transducer element was a single bridge probe with a wall of 7 mm and the cross sectional area of the cone was 15 cm2, having a penetration velocity of 1.5 m/min. The results were recorded automatically. Comparison of the data obtained before and after the quake is shown in Figure 14. Comparison of the data on the saturated sand layers above the depth of 5.4 m is listed in Table 4. The specific cone penetration resistance of saturated fine and moderate sand layers above the depth of 5.4 m was found to decrease after the quake. This implies that sand layers to a depth of 5.4 meters were loosened by the earthquake. The sand below the depth of 8 meters was found to have densified somewhat.
(3) Correlation between SPT and SCPT results. For the saturated uniform, fine and medium sands at the Lujiatuo Mine, the functional relation between corrected SPT blow counts, N63.5, and specific SCPT resistance, Ps , is determined by statistical analysis (Curve 1 in Figure 15):
P Ns = +1151 652 635. . .
The correlation coefficient of g = 0.9 indicates a strong correlation between the two. In addition, similar correlation curves from Japan, India, Greece and the U.S.S.R. are also plot-ted in Figure 15 for comparison. Because the cone top resistance was plotted against the standard penetration resistance (or blow count N) for all foreign data, it is reasonable that Curves 2-4 from the foreign data are situated below Curve 1.
(4) Soil properties
1) Physical properties of clayey soils in the surface layer are listed in Table 5. It can be seen that density of the soil decreased slightly after the quake.
2) Physical properties of the saturated fine and moderate sands and the relative density derived from N63.5 value are listed in Table 6.
Data in Table 6 show that the saturated sands at the Lujiatuo Mine are fine and uniform with relatively low densities. This implies low resistance of this sand to earthquake-induced liquefaction.
3) The clayey soil at 5.4-7.1 m below the ground surface had low plasticity and changed into light loam at the depth of 7.1-7.7 m. Their liquidity index ranged from 1.11-1.43. This indicated that they could be in a flow and plastic state and liable to vibro-liquefaction. The static cone penetration test results obtained before and after the quake showed that the soil had densified somewhat after the quake (Table 7). At the depth of 10.1-13.7 m, the plasticity index of the soil was 11 and that of the light loam usually about 9. The gradation analysis indicated that 30 to 33% of the soil had grain size greater than 0.05 mm and 17-21% of the soil had grain size smaller than 0.005 mm and was classified as clayey soil. The soil was not susceptible to liquefaction, particularly for the soil with high clay content and with sand con-tent less than 40%.
Although this soil had not liquefied, the SPT drill rod under a static load of 63.5 kg weight fell 10 to 15 cm when it reached the top of the layer and the penetration of the first
482
blow was quite large, up to 20-39 cm. This happened frequently in the area where liquefac-tion was serious.
4) The saturated silty sand layer below the depth of 7.7 m was slightly densified after the quake. Such densification of the soil after the quake can be estimated using the specific penetration resistance from the static cone penetration tests (Figure 14). Ps values of the soil ranged from 135 to 150 kg-force/cm2 and the soil was still a stable dense sand after the quake.
(5) Effects of effective overburden pressure on liquefaction. The ground surface at the Lujiatuo Mine is quite flat and the groundwater hydraulic gradient is very small. The Tangshan earthquake occurred during the rainy season and the water table was about 1.2 m below the ground surface. The groundwater table during the exploration (April 1977) was 1.7 m and the head difference was only 0.5 m. Thus, the ground topography and the ground-water table either had not changed or had not changed much from the time of the quake to the time of the exploration. The foundation soil was quite uniform in the horizontal direction. When neither density nor sand content varied much, the overburden pressure became an important influencing factor for liquefaction. The liquefaction at the site, in fact, was serious in the eastern and the western section where the overburden pressure was small, but mild in the central area where the effective overburden pressure was comparatively greater. The curve in Figure 16 shows the variation of the effective overburden pressure in the west-east direction. The boundary value of effective overburden pressure between the lightly liquefied area and the seriously liquefied area is 0.4 kg force/cm2. This shows that the initial overburden pressure does affect the liquefaction resistance of soil to a certain extent.
There is another similar example. The working area of the Fangezhuang Mine and the proposed site for the Coal Processing plant, close to the west of the working area, were sites both located in the area of intensity IX. Both the particle size distribution and the relative density of sand at these two sites were similar. At the Coal Processing Plant, the sand layer was exposed without an overlying layer and the water table was close to the surface. Severe sand boils at the site indicated serious liquefaction. To the west of the mine shaft located next to the plant, there was an overlying layer 0.8-1.5 m thick over the sand layer with an effective overlying pressure of about 0.3 kg-force/cm2. The water table was about 2 m deep. Liquefaction was also rather serious at the site. At the site east of the main and secondary shaft entrances, where the sand had an overburden layer of 1.5-2.5 m thick with an effective overburden pressure of about 0.5 kg. force/cm2, liquefaction was quite mild and almost no sand boils occurred.
(Translator: Lu Rongjian)
483
Ta
ble
1. G
radi
ng o
f san
d pa
rticl
es fr
om sa
nd b
oils
.
Sam
plin
g Si
eve
Ana
lysi
s (%
) N
atur
al
slop
e A
vera
ge
parti
cle
Effe
ctiv
e pa
rticl
e In
hom
ogen
eity
loca
tion
>1
(mm
) 1-
0.5
(mm
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5-0.
25
(mm
) 0.
25-0
.1
(mm
) <0
.1
(mm
) in
clin
atio
n (u
nder
w
ater
)
size
(m
m)
size
(m
m)
coef
ficie
nt
Cla
ssifi
catio
n
E-1
Pum
p ho
use
1 2
9 80
8 —
0.
17
0.
105
1.6
Fi
ne sa
nd
E-2
Pum
p ho
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—
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78
9 —
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0.10
2 1.7
Fi
ne sa
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W
-1
Wor
k-sh
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1 2
6 83
8
31°
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155
0.
103
1.5
Fi
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484
Tabl
e 2.
Par
ticle
com
posi
tion
of th
e un
dist
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d sa
nd.
Sam
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eve
Ana
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s (%
) N
atur
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parti
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Effe
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hom
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dept
h (m
) >1
(m
m)
1-0.
5 (m
m)
0.5-
0.25
(m
m)
0.25
-0.1
(m
m)
<0.1
(m
m)
incl
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ion
(und
er
wat
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size
(m
m)
size
(m
m)
coef
ficie
nt
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ssifi
catio
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2.3
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1
11
83
5
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38
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4.6
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77
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oder
ate
sand
(L
ight
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low
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8.1
4
6
21
57
16
—
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76
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83
2.4
2 Fi
ne sa
nd
(Gre
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gr
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485
Table 3. Comparison of standard penetration blows, N63 5. , before and after the quake.
Depth (m) N63.5 (Individual value /Ave. Value) Difference of blows*
Decrease rate (%)
Before the quake After the quake ∆N DN Nbefore the quake/ 1.5-2.5 8-9.5/9 7.2-8.7/8 -1 11.5 2.5-3.5 9.5-12.7/11.1 8.7-11.5/10.1 -1 9 3.5-4.0 12.7-15.5/14.1 11.5-12.7/12.1 -2 14.2 4.0-5.4 14.5-15.5/15.0 7.5-12.7/10.1 -4.9 32.7
*"-" indicates that the average blow count after the quake is Less than the blows before the quake
Table 4. Specific penetration resistance, Ps , before and after the quake.
Ps (kg –force /cm 2 ) Decrease Depth (m) Before the quake After the quake ∆Ps rate (%)
1.5-2.5 64-83/74 49-76/63 -11 14.9 2.5-3.5 83-97/90 76-90/83 -7 7.8 3.5-4.0 97-104/101 86-90/88 -13 12.9 4.0-5.4 104-113/109 57-86/72 -37 33.9
Table 5. Physical properties of clayey soil in the surface layer.
Index Testing time
Water content
Vol. Weight (g /cm3)
Dry vol. wt. (g /cm3)
Porosity Degree of saturation
Before the quake 21.9 1.91 1.57 0.71 82
After the quake 22.2 1.88 1.54 0.77 78
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Table 6. Physical properties of saturated sand layers.
Effective Relative density Index
Depth (m) particle
size (mm) Ave. particle
size (mm) Inhomogeneity
coefficient Before
the quake After the
quake Variation
1.5-2.5 0.11 0.185 1.85 0.63 0.60 -5 2.5-3.5 0.11 0.186 1.78 0.72 0.68 -6 3.5-4.0 0.12 0.230 2.02 0.76 0.72 -5 4.0-5.4 0.12 0.266 2.58 0.73 0.66 -10
Table 7. Ps value for the clayey soil and the light loam.
p kg force cms ( / )- 2 Difference of Depth (m) Name of soil Before the
quake After the
quake Ps Values
(kg-force /cm2)* 5.4-7.1 Clayey soil 8 11 +3 7.1-7.7 Light loam 11 16 +5
*Plus sign indicates that ps value after the quake is greater than that before the quake.
Figure 1. Geographic Position of Lujiatuo Mine.
487
1. Main shaft; 2. Bye-shaft; 3. Main workshop of the coal processing plant; 4. Boiler; 5. Peat precipitation tank.
Figure 2. Schematic diagram for the working site of Lujiatuo Mine.
Figure 3. Fracture of the raft foundation of the winch workshop in the main shaft of Lujiatuo Mine
488
Figure 4. Arrangement of peat precipitation tanks (Elevation: m; size: mm).
Figure 5. Construction of the rail wall(Elevation: m; size: mm).
489
Figu
re 6
. H
oriz
onta
l rel
ativ
e dr
ift o
f the
rail
wal
l and
diff
eren
tial s
ettle
men
t of t
he ra
il.
490
Figure 7. Crack and local depression occurred in the bottom slab of No. 4
main tank.
H–depth(m); N63.5–standard penetration blow count; e–penetration; γ –volume weight (g/cm3)
Figure 8(a). Log diagram for the secondary shaft well of Lujiatuo Mine
Figure 8(b). Cracks on the secondary shaft well of Lujiatuo Mine.
491
Figure 9(a). Foundation of the main shaft of Xujialou mine and the Log diagram (unit: m).
Figure 9(b). Schematic diagram showing cracks on the vertical shaft foundation (mm).
Figure 10. Geological profile of the shallow layers of Quaternary System in Lujiatuo Mine.
492
Figure 11. Comprehensive log diagram of the shallow layers of Quaternary System in
Lujiatuo Mine.
Boring hole protected by slurry and rotating boring used; 2. Boring hole protected by sleeve
and impact boring used; solid lines are the critical values given in the Chinese code.
Figure 12. Comparison of blows in the standard penetration tests by use of two kinds
of boring respectively
The critical line for the area of intensity VII; 1. curve.obtained before the quake; 2. curve obtained after the quake; 3. curve for the depression area obtained before the quake; D . blows obtained before the quake; O. blows obtained
after the quake; x. blows for the depression area before the quake Figure 13. Curve for the relationship between the standard penetration blow count (N63.5)
and the depth before and after the quake
493
Curve obtained before the quake; - - - Curve obtained after the quake; × Specific penetration before the quake; ° Specific penetration resistance after the quake; ⊗ Deleted specific penetration resistance value before
the quake; • Deleted specific penetration resistance value after the quake.
Figure 14. Specific penetration resistance (ps)Vs depth (H) before and after the quake.
Curve of this paper; 2. Empirical curve of Japan; 3. Empirical curve of U.S.S.R.; 4. Empirical curve of Greece and India
Figure 15 N63.5 versus Ps.
Figure 16 Effective overlying pressure (s v ).
494
DAMAGE TO FOUNDATIONS IN THE METROPOLITAN TIANJIN AREA
Huang Xiling,1 Cui Jingli,2 Gu Xiaolu3
1. Earthquake damage to foundations and its relation with engineering geology.
Tianjin is located in the north of the Northern China Plain, facing Bohai Sea in the east. Relief of Tianjin is low, and its elevation is only a few meters above the mean sea level. For thousands of years, rivers have changed their courses and the coastline has shifted many times. This geological process has resulted in an extensive area with alternate alluvial and marine deposits. The Tangshan earthquake caused catastrophic ground failures, such as extensive sand boils, landslides, ground fissure and settlement of highly compressible soft clay deposits in most of the urban and rural areas of Tianjin. The ground failures led to the collapsing and tilting of many buildings, sliding and slumping of river banks, severe cracking and settlement of highway and railway embankments and dams, extensive cracks of highway pavement due to differential embankment settlement, displacement and failures of bridges, and burial of farm land and blocking of wells and culverts by the sand brought to the ground surface by sand boils.
Sand boils resulting from the earthquake-induced liquefaction of saturated fine silty sand caused buildings to settle 10 to over 30 cm and to tilt from 5% to 15%. Extremely large dif-ferential settlement caused serious cracking of buildings. Foundation failures were not observed in Tianjin where the water table was shallow at about 0.8-1.5 m below the ground surface.
The statistics of the Tianjin Planning Bureau gave 58 sand boil strips in the urban area (Table 1). The distribution and the amount of surface sand were different for different areas. For example, at the courtyard of the Tianjin Wool Mill, there were about 1,000 sand boils with diameters ranging from 1 to 4 m and heights of about 50 cm.
Landslide-induced ground fissures were extremely destructive. All buildings, highways, railways and embankments where fissures ran through were seriously damaged. The length of fissures reached up to several hundred meters and their width reached tens of centimeters. Fissures developed along banks of existing rivers and old river channels or in the vicinity of pits. Fissures were generally parallel to river banks and the side of pits, and they mostly occurred in the vicinity of bank slopes. Sand boils were often accompanied by ground fissures. Landslides in the vicinity of fissures caused buildings and trees, etc., to tilt along the direction of the landslide.
1 China Academy of Building Research 2 Tianjin Institute of Building Science Research 3 Tianjin University
495
The investigation by the Tianjin Planning Bureau showed 80 ground fissures with length and width reaching 800 m and 0.9 m, respectively (Table 2). The fissure at the T. B. Preven-tion Hospital in Liulin was 0.9 m wide and had a maximum off-set of 1 m. The fissure caused serious damage to both the superstructure and foundation of the hospital.
In districts facing the Bohai Sea, such as Hangu, Xingang, Beitang and south suburb, there were extensive silty soil layers of marine deposits with void ratio exceeding 1.3, water content greater than 45%, compressibility coefficient of 0.15, and the bearing capacity around 6 to 8 ton-force/m2 (even 2-3 ton-force/m2 in some areas). Under the building dead load, settlement reached as high as 30 to 50 cm. During this earthquake, settlement and tilting of buildings occurred suddenly. For example, a group of buildings in Xingang district (four-story apartment buildings) completed in 1975 experienced a maximum settlement of 47 cm under their own dead load prior to the earthquake. During the earthquake, buildings suddenly settled an additional 38 cm and tilted for 30%. Ground surface at the pump station of a fertilizer plant in Hangu district settled 38 cm, causing rupture at pipe connections.
It is very important to better understand the local geological conditions, because they are closely related to the nature of failures of the foundation soils. In the areas from Hezhuangzi (Liulin) to the Wool Mill and around Meimang Building and Tianjin Hospital are the old channel areas of the Haihe River; around Tuanjie village in Dingzigu is the old channel dis-trict of the Daqinghe River (Fig. 1); around Yaoyang Road, Hanyang Road and Liuzhou Road are the clay deposits of the Haihe River. No. 2 steel Refining Plant and Xixin Cotton Mill are located near the bank of the Yueyahe River and the Haihe River, respectively.
Seven old buried channels and 45 old water pits cover 4.7% of Tianjin City. Alluvial deposits, miscellaneous fill land and pure fill land account for 6.2%, 12.6% and 31% of the city land, respectively. Silty soils cover only limited area in Tianjin. In Tanggu and Hangu districts, marine silty soils cover large areas. There were large amounts of newly deposited soil layers on both banks of the existing rivers, mostly in these new deposits. Old river channels are divided into three zones, i.e., mid channels, sloping and mid-meander belts. While sand boils occurred in all these zones, the nature of liquefaction-induced damage in different zones differed significantly. For instance, extremely deep depressions occurred in mid channels, while landslides and ground cracks occurred on sloping river banks and along the edge of culverts and pits. The majority of liquefaction and sand boils occurred in the mid meander belts. Different types of ground failures had different effects on foundations and the superstructures. Compared with other areas, the old river channel area has the least resis-tance to an earthquake. In the coastal area with silty soils, the strength of foundation soils drastically reduced during the earthquake and buildings suffered excessive settlement and tilt. In the area with alluvials, the ground failures occurred mainly in the form of ground fissures and sand boils. In areas with miscellaneous fills, the damage to buildings like Dayingmen was serious because of insufficient earthquake resistant design. Damage rarely occurred in areas with ordinary soils. Damage to buildings with treated miscellaneous fills was minor.
496
2. Earthquake resistance of building foundation and foundation soils
The damage survey for the area with intensity VII and VIII in Tianjin indicated that the earthquake resistance of foundation and foundation soils could be attributed to many factors. Among them, soil types were found to be most dominating. Foundation soils in Tianjin can be classified into three types: ordinary soils, liquefiable soils, and coastal silt and silty soils.
The ordinary soil refers to natural cohesive soil deposits of the Quaternary period with good earthquake resistance.
The liquefiable soils refer to the saturated loose silty sand and light loam, which experi-enced liquefaction during the earthquake. The subsurface investigation showed one or two layers of liquefiable soils within the top 6 to 8 meters; sometimes up to 11 meters. Sieve analyses showed that the liquefied soils brought to the ground surface were silty sand with less than 5% clay and more than 60% of the soil with grain size greater than 0.05 mm. The borings made in the liquefied area after the earthquake also revealed that light loam with high fluidity and high sand content besides the saturated silty sand. It is very hard to secure undisturbed samples of such soils because of unstable soil structure with cohesive particle content of less than 10%, and the soils are easily liquefiable even under slight vibration in hand.
In liquefiable soils, the porosity, water table and thickness of overlying layers are impor-tant influencing factors for liquefaction. If the water table is deep and the overlying layers are relatively thick, no sand boils will occur even if there are liquefiable soil layers. Soil layers liable to be liquefied extensively exist on the two banks of the existing rivers, in the old river channels, and in the alluvial filled area.
Coastal silt and silty soil refer to the soils in the range of bearing layer, which are mainly silt and silty soil.
Earthquake resistance of the three types of foundation soil mentioned above and the earthquake resistance of pile foundations are described in the following paragraphs.
(1) Foundation on ordinary soil
No obvious damage to foundations on ordinary soil were found in the areas of VII-VIII. In the survey, settlement of buildings was measured after the quake. The additional settle-ment was small, about 1/12 of the total settlement (Table 3), and the superstructure was good in performance. Walls and columns of certain buildings were cracked mostly around ground level and no damage to the foundation was found.
(2) Foundations on soil liable to liquefaction
In the sand boils zone, settlement and tilting of buildings occurred to various extent, but collapse of buildings due to instability of ground soil was not or has not yet been found. In the urban area, thickness of liquefiable soil layer was not so great, and there was an overlying layer of definite thickness above the liquefiable layer. Within the range of the main bearing
497
soil layer, liquefaction might occur individually; while in the local liquefaction area settlement of buildings was comparatively uniform and cracks were seldom found in build-ings. Damage to foundations was also not seen when the distribution of soil layers and lique-faction were relatively uniform. When distribution of sand boils was not uniform, tilting of buildings was liable to occur. When local settlement of buildings occurred due to sand lique-faction, walls would be cracked seriously and foundations fractured. In addition, when ground cracks and differential settlement of ground occurred due to liquefaction, tilting of facilities was commonly found.
(3) Foundations on coastal silt and silty soil layers
Relatively large deformation under vibration may occur on silty ground of very low strength. For example, in Wanhai apartment block of Xingang district, 16 apartments were 3-story buildings and 10 were 4-story buildings. The buildings had raft foundations with a depth of 0.6 m. The allowable bearing capacity of the foundation soil was 3-4 ton-force/m2, but the actual value adopted in design was 5.7 ton-force/m2. The apartments were completed in 1974. Total settlement of the 3-story apartments was 25.3-54.0 cm after the quake, and the difference between the settlements after the quake and before the quake was 14.1-20.3 cm. Tilting before the quake was 1%-3% and after the quake was 3%-6%°. Total settlement of the 4-story apartments after the quake was 28.8-85.2 cm, and the difference between the settlements after the quake and before the quake was 14.6-32.5 cm. Tilting before the quake was 0.7%-19.8% and after the quake 0.7-45.1%. The above example shows that, before the quake, the settlement and tilting of buildings on silt soil had been extremely large, and, after the quake, they suddenly and substantially increased.
In the 1964 Baohai Sea earthquake, intensity in Xingang district was VI. Not much damage to buildings was found and settlement of the ground soil was minor. In the Tangshan earthquake, intensity was VIII+. The settlement of the soft ground of high compressibility and without consolidation, therefore, was relatively large.
(4) Earthquake resistance of pile foundation
A pile foundation is good for buildings built on liquefiable ground. In serious liquefaction areas, most of buildings with pile foundation had no obvious settlement. On the edge of the slope of the river bank, however, piles were damaged when sliding occurred on the slope. Damage to the pile foundation of bridges was mainly induced by the deflection of the pile due to sliding of the soil mass, which then led to displacement or falling of the bridge.
Based on the damage survey for 30 more buildings with pile foundation in the urban area, the following conclusions were obtained:
1) Earthquake resistance of the pile foundation is better than that of the natural founda-tion, with less damage to buildings. For example, triangular piles 9 m in length were used in the 5-story classroom building of the Guizhou Rd. Middle School with alluvial filled land
498
foundation. The building was intact basically after the quake, while all other buildings in the vicinity were damaged seriously.
2) Deformation of pile foundation under vibration is much less than that of natural foun-dation. For example, settlement of the Tianjin Friendship Guest House, with 8-story framed structure and precast pile foundation, increased not more than 1 mm, on average after the quake. In the Petroleum Chemical Product Plant with boring piles in the south suburb, the additional settlements of certain tower-shaped structures were only 4-6 mm after the quake.
3) No problems were found for most pile foundations on liquefiable soil. This resulted from the fact that piles used in the urban area were rather long, penetrating generally to the yellow cohesive soil layer of better capacity. The thickness of the liquefiable overlying layer was not great.
4) Lateral resistance of the pile foundation should be considered. For example, in the boring pile foundation below the trestle column in the Moderate-size Steel Plate Plant, the liquefied soil layer was forced out laterally in the quake due to the excess ground load, lead-ing to deformation of piles and tilting of platform.
5) Although the earthquake resistance of pile foundation is good, some problems also occurred under the effect of the earthquake. For example, two 8-m piles were used instead of one 18-m pile in 12 column foundations of a warehouse in Beitang district. This was due to fracture in pile-driving. Because the pile tips of the 8-m piles were not supported on the same soil layer as the other piles, the 8-m piles settled with the ground; leading to tilting of the platform. Moreover, a portion of the slab supported by the piles lacked underlying soil and owing to the weight of the platform (7 tons), piles were fractured by shear in the connection of the pile and the platform. Some parts of piles remained intact. When the fill was loose around the platform, dislocation would occur on the interface of the loose soil and the compacted soil so that cracks appeared. In the inspection of piles in the warehouse, cracking of piles was found at the bottom of the fill level.
3. Ground fissures and their effect
Large amounts of ground fissures occurred in the quake and these present dangerous problems to foundation. Based on the pattern and the position of the fissure, and the deformation of ground, it appears that most of the ground fissures were induced by relative sliding of the soil mass.
The two banks of the river, the banks of the old river channel, and the edge of the pit of coastal silty clay were developed zones of ground fissures. Orientation of fissures was parallel to the bank and the pit edge approximately. The primary fissure had obvious hori-zontal and vertical offsets. Buildings through which a primary fissure passed collapsed or were seriously damaged, and were difficult to repair. Soil mass between the fissure and the river bank slid and buildings inclined. Causes for sliding varied, depending on morphology and soil properties. In the old river channel area, there still existed old unburied channels, some of which had been used as drainage channels. The exposed plane was comparatively large. On the bottom of the old river bed, there were slopes toward the center of the river
499
always covered by a silt layer liable to flow or a silt layer liable to liquefaction. Ratio of width in the range of developed fissures and the height of the exposed plane was up to 10:1-15:1.
In the alluvial filled area, old water ponds and depressions mostly existed in the original land. The alluvial materials were mud and sand from the river. The water content was 24%-36%, porosity was 0.77-1.11, and the particles were fine and uniform. Because the material filling was carried out in stages, a small earth embankment was built first. Next, mud and sand were filled on a side of the embankment. On the other side, a hole was made to let water out so that coarse particles were deposited around the inlet in the vicinity of the hole. Finally, fine particles deposited around the outlet, making the thickness of the alluvial filled layer varied, and the material non-uniformly distributed. The alluvial filled land is likely to liquefy and form sand boils; the sand boils will most frequently have loose structure.
For banks of recent rivers with no retaining slopes, such as the Haihe River and the Ji Canal, a lot of the sliding occurred of the material along the banks. In the case of the Haihe River; however, the bank slope was normally intact in the urban area where plate piling was used, although many structures had been built on this area.
From the site investigation, strengthening the foundation and superstructure in the recent river and old river channel areas, on which ground fissures would probably occur, was not effective. When the surface layer was a relatively poor silty soil layer or liquefiable soil layers existed, the existing artificial pits or culverts were dangerous. For example, in the No. 2 National Cotton Mill, a pit for a basement of area 30 × 30 m2 was excavated before the quake. When the excavation was being carried out to the depth of 3.7 m, sand flow appeared. After the quake, sand and water blew from the bottom of the pit, and walls of the pit collapsed. In the range of 50 m around the pit, many ground fissures occurred on the surface, and the soil layer under the pit heaved, causing the nearby buildings to crack and collapse.
Compared with the ground fissures that occurred in old river channels and those in the filled river channels, deep pits, and depressions, it is shown that existence of the exposed plane is a critical problem to be solved.
In addition, for the large ground fissure which occurred in Fuzhuang, Hangu district, dis-location on two sides of the fissure was up to 2.6 m; fracturing all deep well pipes. Buildings through which the fissure passed all collapsed. Such ground should not be selected for building sites.
4. Filled land and the effect of land treatment
Many filled lands exist in the urban area of Tianjin. In the old city area, thickness of the filled land is generally 4-5 m, and the thickness gradually decreases from the center of the city outward. On the margin of the urban area, the thickness becomes 1 m or less.
Filled land can be classified as alluvial filled land, pure filled land and miscellaneous filled land according to their composition and engineering properties. In the alluvial filled
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land area, old water ponds and depressions mainly exist. The alluvial materials are mud and sand from the river channel. The main composition of these materials is light loam soil of grayish yellow or yellowish gray color. Because the time of fill is earlier, the allowable bearing capacity of the filled land is up to 8-12 ton-force/m2 , and no treatment of land is required. Pure filled lands distribute mainly on the edge of the urban area and thickness of which is about 0.5-1.5 m. Most of the pure filled lands consist of cohesive soil with little miscellaneous materials. The pure filled land is relatively good for earthquake resistance, and no obvious damage was found in the earthquake. Miscellaneous filled land consists of construction debris, furnace ash, and rubbish. It is complicated in composition and uneven in properties. In recent years, vibro-compacting and vibro-pouring short piles are used for con-solidation.
A 10 ton-force vibration compaction machine of 2 tons weight was used for vibro-com-paction. The settlement under vibration was generally 15-30 cm, and up to 50 cm indi-vidually. Effective thickness of vibro-compaction was 1.5 m and the machine was suitable for thin miscellaneous filled land layer or light-weight structures. The prior-quake settlement of 17 buildings after vibro-compaction was less than 3 cm in average, while that of buildings on the untreated miscellaneous filled land, such as Siping Road Middle School, was up to 22.1-32.6 cm. The walls in the school cracked. After the quake, no obvious deformation was seen on the ground surface of the above-mentioned buildings, and structure of these buildings was basically intact (Table 4).
For relatively thick filled land with silt interlayer and good underlying layer, adoption of vibro-pouring short piles also had better effect for earthquake resistance. There were 8 buildings with the above mentioned short piles, length of which were 4-8 m diameter about 30 cm. For 7-8 years after the buildings were built settlement of the foundation was small, and buildings were in normal service after the quake, no damage to the 3-4-story civil build-ings was found. As for the single-story plant buildings, small cracks on walls occurred locally, and developed slightly after the quake.
5. Conclusion
The main cause for damage to foundations in the urban area of Tianjin is sand liquefac-tion. Effect of slope sliding on the liquefied ground, that of the sliding ground fissures on damage to buildings, is most serious. Damage to foundations has a dependence on locality. In the old river channel, pit and pond, and alluvial filled land areas, sand boils occurred and extreme ground cracks developed. On coastal soft clay, depression due to the earthquake was large. On ordinary foundation soil, pure filled land and artificially treated miscellaneous filled land, damage was slight. Damage to foundations on ordinary soil was much less. On liquefiable soil, damage to foundations was different. Raft foundation is good for regulating the differential settlement of the foundation and strengthening the superstructure against earthquakes. Earthquake resistance of pile foundation is also good.
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Table 1. Sand boils in Metropolitan Tianjin.
Name of district
No. of sandboil
strips
No. of sandboil locations
Max. amount of spouted sand in
a strip (m3)
Color and classification of spouted sand
Heping district 26 120 15 10 strips of yellow or brownish yellow color; 5 strips of gray or grayish yellow light loam
Hexi district 16 850 80 2 strips of yellowish gray color; 14 strips of grayish yellow, gray silt and light loam
Nankai district 2 more than 50
64 Yellowish brown silt
Hongqiao district
2 in groups large amount Yellowish gray and yellowish brown silt
Hebei district 5 8 10 Grayish yellow and gray silt
Hedong district 7 more than 3000
4000 Grayish yellow and gray silt and light loam
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Table 2. Ground fissures in the urban area of Tianjin.
Name of No. of Data on fissures Sand boils induced by district fissures and
locations Direction number Max.
Length (m)
Max. width (cm)
ground fissures
WE 1 5 2 32 locations NS 2 20 3 accompanied with sand
Heping 55 nos.and NNE 21 100 10 boils, and in 8 of which district 46
locations NNW 10 400 5 sandboils occurred
NWW 9 80 5 seriously NEE 5 100 3 WE 3 50 7 15 locations accom
Hexi 26 nos. and NS 1 70 2 panied with sandboils, district 20
locations NW 19 540 5 and in 8 of which sand
NE 3 40 1 boils occurred seriously
Nankai 4 nos. and NE 3 180 5
2 locations accompanied with
sandboils, and district 4 locations
NW 1 60 5 in one location
sandboils occurred seriously
Hongqiao 2 groups
and 2 NW 1 group 1000 30 Group of sandboils
occurred in the district locations NE 1 group 30 50 two sides of fissures in
one location Hebei district
1 no. and 1 location
NNE Sand boils occurred nearby of fissures
NE 2 700 90 Hedong 7 nos. and NW 1 100 3 A lot of sandboils district 7 locations NS 2 800 5 occurred
WE 1 20 5 (Translator: Lu Rongjian)
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Table 3. Settlement of buildings on ordinary soil measured before and after the quake.
Name of building Tianjin Hospital ward Department
Tongshan Lane Apartments
Office Building of Material
Bureau
Type of structure 7 -8 story precast frame
6-story composite structure
6-story composite structure
Allowable bearing capacity of the bearing layer /actual allowable bearing capacity used in design
12/12 12/11.25
Difference of settlement before and after the quake(mm)
26-38 8.56-11.32 9.42-11.22
Accumulated settlements after the quake(mm)
253.6-384.8 95.24-146.39 114.97-137.57
Lateral Before the
quake 2 4.7-8 0.84-1.28
inclination(%) After the quake
0.16 (opposite direction)
8.1-8.2 0.95-1.52
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Table 4. Damage to the miscellaneous filled land foundation after vibro-compaction.
Name of building
Outline of building and
structure
Outline of foundation and construction
Design bearing capacity
(ton-force /m2)
Damage to building after the quake
Cleaning Workshop, Tianjin Diesel Plant
Single story building of brick-wood structure, concrete floor of 10 cm thick, brick foundation with foundation beam and ring beam
Originally, a pond for planting lotus, 3-4 m. deep, with a filled layer of crushed bricks, tiles and slags, composed of organic slurry, etc., inbrated by cranes, vibro-compacted for 3 times
10 Wooden beam pulled out from the gable wall only
Decorating Workshop, Diesel Plant
Single story building with a mezzanine floor for offices, R.C. stripe foundation, with ring beam
Foundation same as above, vibrated by modified driving machine, built in winter
10 Intact
Diesel Body workshop, Diesel Plant
A mezzanine floor for offices, rigid portal frame, column foundation of 2.5×3.2m, loading: 39 ton-force
Same as Decorating workshop
10 Intact
Staff dormitory, Tianjin Machinery Plant
3-story building with R.C. stripe foundation
Originally, a rubbish pit containing ash mainly, extremely loose, under the pit is a clayey soil layer of 0.2-0.4m thickness, depth of the pit: 3m
10 no cracks
Coiling workshop, Firing Coil Plant
2-story composite structure, R.C. stripe foundation
Debris and rubbish 3.5-4.5m thick, loose, underlying clayey soil
no cracks
Repairing workshop, west Long-distance Bus station
Single story plant building, thin-web beam, one ring beam
Furnace ash and rubbish at the end of 1/3 length of the building, the remaining part is natural ground
10 Intact
Two 3-story workshops, No. 2 Wood Product Plant
Inner framed structure, with 1½ B columns in the middle, R.C. stripe foundation
Originally, a pit for slag and ash, 2m deep, extremely loose in individual location, very uneven in layer
10 Inclined cracks on wall induced by horizontal seismic force, no cracks on the foundation due to settlement
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Table 4 Continued.
Name of building
Outline of building and
structure
Outline of foundation and construction
Design bearing capacity
(ton-force /m2)
Damage to building after the quake
A workshop in No. 3527 Plant
Single-story plant, Part is raft foundation for a 100 t equipment, the remaining part is R.C. stripe foundation, two ring beams
Originally a rubbish pit, 3.5-4.0m deep, distance between the underground water level and the bottom of the equipment foundation is only 20 cm approximately
10 Intact
Past Mixing workshop, No. 1 Printing Plant
Single story, 3 bays, brick stripe foundation, ash soil under the foundation, with ring beam
Originally a water collecting pit with no obvious margin, a furnace ash layer in the bottom, part of the soil is silt, depth of the pit:4. 2m
10 Building cracked before the quake due to drawing of underground water in the nearby building, cracks developed after the quake, not related to foundation settlement
5-story dormitory, municipal Material Retrieving co.
Composite brick structure, R.C. stripe foundation
Miscellaneous filled pit 2.2-3.7m deep, containing crushed bricks, ash and rubbish, under which is a clayey soil layer
10 Cracks due to poor workmanship, foundation soil treated well, settlement 3 cm in average
4-story class-room building in Chengdu Road
Composite structure
Originally a rubbish pit 10 Intact
Cafeteria in No. 512 Plant
Portal frame, column foundation, 2 ring beams
Originally a pit 3.5-3.7m in depth, under which is clayey soil, allowable capacity of the underlying layer is 6 ton-force/m2
8 Intact basically
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Figure 1. Old river channels and damage to ground surface from Hezhuangzi (Liulin) to the woolen mill.
Figure 2. Distribution of the newly deposited soil in Tianjin.
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DAMAGE TO PILE FOUNDATIONS IN TIANJIN
Wu Jiaxun*
1. General
Tianjin faces the Bohai Sea in the east. The ground is low and depressed, with soft, loose soil. Frictional pile foundation is mostly adopted in all kinds of building structures. Excluding the wharf area in the harbor, low and straight piles are commonly used in the industrial and civil buildings; for most of which no measures against earthquake were adopted.
In the industrial and civil buildings, round wood piles and precast rectangular RC piles were often used before and in the early stages of liberation. After that, precast RC piles and poured piles were mainly used.
Investigation shows that, before the Tangshan earthquake, structures with pile foundation in Tianjin were generally in accordance with the requirements.
After the quake, related departments had been organized by the Tianjin municipal con-struction committee for the survey of damage to structures with pile foundation in the Tianjin region. Statistics of the investigated industrial and civil buildings, totaling 100 in number, are summarized in Table 1. In the above structures, 7% had damage to the superstructure with only slight damage to the pile foundation, 3% had damage to the pile foundation only (of which two pile-supported platforms had recently been completed), and the remaining structures with pile foundation remained intact. It can be concluded that pile foundation exhibits good earthquake resistance; some characteristics of earthquake damage to certain structures are described as follows.
2. Typical cases of earthquake damage
(1) Slight damage to the superstructure and pile foundation
1) Class-room building of the Guizhou Road Middle School
a. General
The building, completed in 1966, was a five-story composite structure, the plan of which is shown in Fig. 1. The central portion of the building was used as the staircase and the entrance hall, while the other three wings were used as classrooms and offices; settlement
* Tianjin University
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joints were kept between these four sections. Total height of the building was 17.19 m, with a building area of about 5000 m2. A 180 × 240 mm spandrel beam was placed on the external wall in each story, #50 lime-cement mortar was used for laying the wall, and floor slabs were precast hollow. There were no checks for earthquake resistance performed in the original design of the building.
Detail of the foundation soil is shown in Fig. 2(a) and (b). In the upper portion, there were relatively thick layers of miscellaneous filled land, silty soil and hydraulic fill. Trian-gular, precast, RC hollow piles of 9 m in length were used (Grade of concrete, 300). Piles were arranged in two rows, with an RC platform beam on top of the piles.
Static loading and dynamic driving tests were performed to determine the bearing capac-ity of a single pile. Arrangement of test piles is shown in Fig. 1. Dynamic driving tests were only carried out for the No. 3 and No. 4 piles. Based on the load curves vs. settlement obtained in the static loading tests, the failure and the ultimate loads of the No. 1 test pile were 34 and 32 ton-forces respectively. Owing to limitation of the loading condition, the No. 2 test pile had not been loaded to failure (only approached to failure), and the ultimate load was estimated as 38 ton-force.
A 1200 kg-force diesel driving machine was used for driving. When an expected driving depth was reached for each test pile, the average penetration of the last 10 blows was recorded. After this initial driving test, the pile was kept at rest for more than 10 days, then driving was repeated. The average penetration of the last 10 blows in the second driving test was also recorded. The ultimate bearing capacity of No. 1 and 2 test piles is listed in Table 2. In the design, the allowable capacity of a single pile was taken as 14 ton-force, and the factor of safety, about 1.64.
b. Earthquake damage
No cracks on the exterior wall were found, and connection between the apron and wall was intact.
One crack was found on the transverse beam of the staircase in the first floor hall. An inclined crack was also found on the transverse wall in one of the classrooms on the same floor; no other cracks were observed. The building was continued in service, and no strengthening was needed after the quake.
Seismic intensity in the local area was VIII, causing serious damage to building in the vicinity. There was soil liquefaction evidence around the classroom building. The old 2-3-story residential buildings around Sashi Road and Yaoyang Road were built on natural foundation. Owing to the soft and loose soil, cracks had already occurred in certain buildings prior to the quake. After the event, most of the buildings were damaged seriously, and a few even collapsed. A newly built 3-story composite structure in the Heping Pharmacy Plant, 10 m from the school to the north, was built on natural foundation soil as well (having a frame in the interior), and part of the filled walls was damaged seriously.
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2) The 5-story large-size panel apartment buildings in Zhangguizhuang
a. General
The plan of the building is shown in Fig. 4. Prior to the Tangshan earthquake, building A was completed and the pile-supported platform was finished only in building B (in Fig. 4, (I), (II) indicate units of the building).
The site soil of the buildings is soft and weak, and the surface layer is industrial waste (fly ash) recently filled to a thickness of 2 m approximately. The upper layer consisted of silty soil and light loam, with a very shallow underground water level. Soil conditions in the foundation are shown in Tables 3 and 4.
In the foundation, RC piles, 9.10 m long, with a triangular cross-section (length of each side, 400 mm) were used. Main reinforcement of the pile were 3 No. 16, stirrups, No. 4, with different spacings: 200 mm in the center; 100 mm near two ends; and 50 mm at the extreme end. Design grade of concrete was 300# . The pile-supported platform was 600 mm wide, 750 mm high, and the platform beam was an RC inverted T beam with 4 No. 12 reinforce-ment.
The static loading test results for a single pile are shown in Fig. 5. Ultimate bearing capacity of single pile was 46 ton-force, and allowable bearing capacity was 21.6 ton-force.
b. Earthquake damage
No damage was found in building A, but ground fissures were observed on the surface outside building B. The ground settled about 10 cm, and the fly ash on the surface was thrown into the water pit in the neighborhood. The bottom surface of the pile-supported plat-form separated from the soil layer surface, as shown in section A-A in Fig. 4, but the platform beam was intact. Construction was carried on after the quake.
3. Cold storage in Hongqi Road
a. General
Construction of the cold storage building started in 1972, and the storage was put in service in 1974. It was a 6-story building with a total height of 22.56 m, having a 7200 ton storage capacity. Elevation of the basement floor was -5.35 m. Column spacing of the building was 6 m × 6 m, and the building area, 13,380 sq. m. A column-supported floor was used in the building. In each story, a spandrel beam was adopted to connect with the floor. The thickness of the floor was 200 mm generally, with 2 No. 10 reinforcement, spacing 200 mm. Section of columns was 400 mm × 400 mm. The foundation was raft foundation, con-sisting of a slab 400 mm thick, 1350 mm × 700 mm cross section beams, and precast RC piles under the slab. There were 17 piles under the central column, and 19-22 piles under the exterior and corner columns. A total of 1256, 15 m length, piles were driven, with a cross-section of 300 mm × 300 mm and 4 No. 6, 3 No. 14 reinforcement. Based on the static loading test results of single pile, the ultimate load was 60 ton-force, and design allowable bearing capacity was taken as 30 ton-force.
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The measured settlement before the quake was 3.4 cm. Boring results reveal that the upper part of the foundation soil is filled land, silty soil and clayey soil. Properties of the soil are shown in Table 5.
b. Earthquake damage
Capacity of the cold storage reached 7800 ton (overloading) before the quake, and was 3500 ton at the time of occurrence. After the quake, cracks occurred in the north-east corner and the south-east corner of the cold storage, and 2-3 locations in the floor beam cracked. No serious damage to the interior of the storage was found. Only in the 1st and 4th stories, rice hulls used for insulation were forced to flow out from cracks of the wall. The accumu-lated settlement was 4.2 cm after the quake.
The intensity was estimated as VII, no damage to the pile foundation was discovered.
In the vicinity of the cold storage, a new 10,000 ton cold storage building was built in 1974 and completed in March, 1976. It was a 6-story structure with column-supported floor, 6 m × 6 m column array, and total height of 31.9 m. The infrastructure was individual column foundations, connected by column beams. Precast RC Piles, 14.5 m long, with a cross section of 350 mm × 350 mm, were under the columns. There were 18 piles under the central column foundation, 19-22 piles under the exterior columns, and 24 piles under the corner columns. Allowable bearing capacity of a single pile was 38.5 ton-force.
The foundation soil was similar to that of the 7000-ton storage.
Damage to the 10,000-ton cold storage was extensive. The inner lining wall collapsed and the rice hull insulation flowed out, as occurred in the 7000 ton storage. Air-entrained concrete partitioned walls were damaged seriously, cracks occurred on the exterior walls above the third floor, and roof beams fell down.
No damage to the pile foundation was found.
For example, average settlement of the main building of the Tianjin Friendship Hotel was 4.0 cm before the quake, but the average additional settlement was less than 1 mm after.
In the industrial buildings, such as Petroleum Chemical Product Plant in the south suburb district of Tianjin, boring poured piles of 600 mm in diameter and 15 m, 18 m and 24 m in length respectively were adopted. Average settlement was 5 mm after the plant was com-pleted in 1975, and then put in operation, and the average additional settlement due to the quake was only 0.4 mm.
The DDT workshop building of the Tianjin Chemical Products Plant in Hangu district was a 5-story framed structure, with a total height of 15.63 m and column arrays of 3.4 m × 2.7 m. The soil at the site was loose and soft. The surface layer was miscellaneous filled land of a thickness about 1.5 m, the next layer was clayey soil and clay, about 2 m thick, and then the light loam and silty clayey soil layer, 5 m thick approximately. Pile foundations were used in the old plant building, with wood piles 12 m in length. Later the building was expanded, but was still a 5-story framed structure. Raft foundation was used for the expanded portion, and a settlement joint was installed between the new and the old building.
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The relative vertical offset between these two buildings at the joint reached 30 cm after the quake. It is obvious that the settlement of the raft foundation was relatively large, and the new building inclined slightly toward the old one. Walls at the joint cracked, and cracks also occurred on individual beams and columns. In buildings with pile foundations in the Tiangjin Chemicals Plant, additional settlement induced by the quake was about 1-2 cm, but that for the RC strip foundation on natural soil was 10-30 cm.
(2) Serious damage to the superstructure, but slight damage to the pile foundation.
1) Hull workshop of the Xingang Ship-building Plant
a. General
The Ship-building Plant was situated on recent hydraulic filled land on the north shore of the harbor. The hull workshop was completed in 1975, with a total length of 174 m. Struc-tural layout of the workshop is shown in Fig. 6. Large size roof panel and prestressed arch truss were used in the roof system, RC web beam was used as the crane beam, and the column was I-shaped with a thin web with openings. Size of the exterior column was 600 mm × 1200 mm, thickness of the web 120 mm, reinforcement in the flange were 10 No. 25, and size of small columns was 600 mm × 600 mm. Two 30-ton cranes were arranged in the exterior bay and two 50-ton cranes in the middle bay. In the middle bay, a bracing system was installed. Design of the structure was based on intensity VII. Earthquake resistant measures were taken for the layout and in the structure.
The site soil is loose and soft. Pile foundation was adopted: four piles supported plat-forms for the exterior columns and six piles supported platforms for the central columns. Precast square RC piles with a section of 450 mm × 450 mm and a length of 23.5 m were used. Main reinforcement of the pile were 8 No. 22, stirrups No. 6 with a spacing of 60 mm in the central portion.
Boring data show that the upper layer was silty soil, with an intercalation of light loam. Bearing capacity of the foundation was very low. Soil conditions can be seen in Fig. 7 and Table 6.
b. Earthquake damage
Roof systems in the side bays, e.g., (1) and (3) in Fig. 6, almost collapsed completely, leaving only one truss at the expansion joint intact. In the middle bay, i.e., (2) in Fig. 6, columns in the two central rows tilted seriously, with a maximum longitudinal drift of 350 mm. Bottom parts of the central bay columns in the higher bay were almost crushed or rein-forcement in the columns exposed; and distortion of the main reinforcement could be observed. No obvious damage to the pile foundation and platform was found.
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2. 200-ton water tank in the Engineering Machinery plant
a . General
The plant was situated in the vicinity of the old channel of the Haihe River (the old chan-nel was left to be cut off in 1921 after realignment of the Haihe River). The soil at the plant site is shown in Tables 7-9. Soil layers, above elevation −11.0 m, were mainly composed of clayey soil, light loam and silt, of which the thickness of light loam and silt was about 12 m.
The 200-ton water tank was completed in 1965 (by use of the standard drawing for 200 m3 water tank with brick support (shui-55), issued by the Ministry of Railway, China). Total height of the tank was 34 m, with a brick cylinder and an RC tank. The tank was 6.20 m in internal diameter and 8.4 m in external diameter (Fig. 8). The foundation was an RC octago-nal plate foundation, the minor diameter of which was 12.2 m. Piles used in the foundation were precast RC driven piles with a cross-section of 300 mm × 300 mm. Depth of the pile toe was -13.8 m and length of the pile was 11.3 m. A total number of 97 piles was driven. 1.5 m depth of water was stored in the tank during the quake.
b. Earthquake damage and measures taken against earthquake
In the main shock and aftershocks, water with sand spouted several times in the plant district. The number of sand boils was ∼ 200. Ground in one of the rooms heaved up to 40 cm, and differential settlement happened in many workshops. Around the foundation of the tank, there were 5 sand boils. Damage to the brick cylinder supporting the tank was serious, with an offset of 220 mm displacement of the top; 170 mm as shown in Fig. 8. Maximum width of cracks on the tank was 400 mm, and the maximum length, 20 m. Cracks were developed symmetrically. The cylinder bulged in the south direction, and the lower part of the cylinder was crushed seriously with scaling on the wall.
After inspection, no tilting or displacement was found for the tank foundation, and it appeared that the pile foundation was still in normal condition.
After the main shock, the cylinder was strengthened by use of jetcrete with reinforcement arranged around the exterior of the cylinder. When the jetcrete was finished, another strong aftershock occurred on Nov. 15, 1976. At that time, the underground portion of the cylinder had not been strengthened. In the inspection, it was found that circular cracks occurred at the connection of the brick cylinder and the RC foundation in the north-south direction at a depth-0.5 m from the surface. The strengthened part of the cylinder was intact.
(3) Damage to the pile foundation in the liquefied soil where the pile tip had not been driven to the stable layer
The product warehouses of the Foreign Trade Bulk Sugar Storage in Tangu district
a. General
The Warehouses were built starting in 1974. Just before the Tangshan earthquake, the pile-supported platform and foundation beams had been completed. Plan of the pile founda-
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tion is shown in Fig. 9(a) and (b). There were two warehouses, No. 1 and No. 2, 15 m apart. There were two bays in each warehouse, with a total span of 24 m. Spacing of columns was 6 m and the exterior columns were connected by the foundation beam of 250 mm × 450 mm cross section. In the design, two precast RC piles were placed under the column foundation. Piles were 18 m long with a triangular section, the side of which was 450 mm. The pile was divided in two parts, 9 m long each. Main reinforcements of the pile were 3 No. 18, and No. 6 stirrups, with various spacings; 200 mm in the middle and 100 mm at the ends. The design bearing capacity of a single pile was 35 ton-force. The top of the pile extended out of the platform for 100 mm, and a network of No. 12 with a spacing of 200 mm was arranged in the bottom of the platform.
During the pile driving process, parts of the pile fractured due to inadequacy of concrete strength when they had not been driven to the design depth. Lengths of the fractured piles were 11 m and 12 m and positions of fracture on the pile are shown in Fig. 9(a) and (b). On two sides of the fractured pile, a supplementary triangular pile of 9 m in length was driven respectively, and the pile-supported platform was changed to be a trapezoid shape platform [Fig. 9(c)].
The storage was situated in the vicinity of Beitang, Tanggu district. The foundation soil was soft and loose, and properties of the soil are shown in Tables 10-11. It is seen that the pile tip had passed through the silty soil and light loam layers into the clayey soil and clay layers, while the fractured pile and the supplementary pile rested in the silty soil layer and the liquefiable light loam layer.
b. Earthquake damage
A lot of long ground fissures occurred at the site. Maximum width of the fissures was up to 0.5 m and orientation was all in WE direction. After the quake, the ground surface changed greatly, and many sand boils occurred at the site, of which 21 were relatively great. Seismic intensity at the site was estimated to be VIII+ .
The platforms of the pile foundation of No. 1 and No 2 warehouses were damaged seri-ously, and foundation beams between the platforms cracked, fracturing by tension. Maxi-mum displacement and relative tilting were 285 mm and 22 cm respectively (Fig. 9a and 9b). It was found that the platform was separated from the surface (about more than 10 cm), and piles were separated from the platform also. After excavation, it was observed that there were 4 cracks on the pile shaft at 1.0-1.5 m from the bottom surface of the platform, the maximum width of which was 8 mm. The platform tilt was serious and damage to the pile shaft was discovered. During the quake, the shallow soil layer was liquefied. The main cause for the above damage appears that tips of the fractured pile and the supplementary pile had not been driven to the stable layer.
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(4) Damage to pile foundation due to overloading of bulk materials
Raw material trestle and product trestle in the Medium-size Steel Plate Plant
a. General
The plant was situated in the east suburb, also in the range of the old channel of the Haihe River, and the geological conditions at the site were similar to the Tianjin Engineering Machinery Plant.
The raw material trestle was completed in 1972, with a span of 33.0 m and a total length of 204 m, as shown in Fig. 10. Spacing of columns in the exposed portion of the trestle was 12 m, elevation at the top of column was +7.35 m and that at the bottom of the crane beam, +6.55 m. Loading capacity of the crane with a span of 31.5 m was 15 ton. The column was a double-member hollow pipe column. The exterior diameter of each member was 400 mm and spacing between the two members was 1100 mm. Under the column was a concave shaped RC foundation, below which were four poured piles of length 15 m, piles were gener-ally redriven once. Diameter of the pile was 620 mm and there were 5 No. 20 inserted bars each 2 m long, uniformly distributed around the pile top and connected with the platform. Size of the platform was 3.0 m × 3.6 m × 1.45 m (height). Loads on the trestle were esti-mated to be 20 ton-force/m2 approximately, but were not uniformly distributed. In the south-east corner of the storing site, water was accumulated for a long time due to depression. Prior to the quake, certain columns had been found to incline inward. Differential settlement of the column foundation was about 10 cm.
The span of the product trestle with a total length of 150 m was 31.5 m, and the spacing of columns was 12 m. Four precast RC piles with a 400 mm square section and 15 m length were driven under each column. The loading capacity of the bridge crane was 15 ton and the actual load on the ground during the quake was ton-force/m2. The soil conditions were simi-lar to those of the raw material trestle.
The plant was located in the old channel of the Haihe River; the soil layers were loose and soft, and relatively thick, including a light loam layer susceptible to liquefaction. Detail of the soil layers and their allowable bearing capacity can be seen in Table 12.
b. Earthquake damage
In the plant area, there were 300 or more sand boils during the quake, and 6 ground fis-sures with the width of 3-5 cm generally.
In the vicinity of the raw material trestle, sand had spouted from the ground several times, and ground fissures developed with a maximum width of 10 cm. Steel ingots piled in the court settled into the ground. The trestle was damaged and a portion of the trestle, about 60 m long near the end, was damaged seriously. Nine foundations tilted inward and dis-placed also. Maximum lateral displacement at the top of the column was up to 22 cm, and that at the bottom was up to 10 cm. Other portions of the trestle were damaged to various extents.
515
Sand boils and ground fissures also occurred in the vicinity of the product trestle. Columns of the trestle tilted inward and crane rails distorted. However, damage to the product trestle was less than that of the raw material trestle, and the former was put into service again after adjusting the crane rails.
(5) Displacement of pile foundation and cracking of pile shaft due to sliding
Turbine workshop of the Institute of Offshore Engineering in Xingang
a. General
The workshop was situated on the south side of the navigation course in Xingang, Tanggu, about 100 m from the harbor to the north and about 50 m from the dock to the east. It was built on a narrow recent hydraulic fill zone, starting at the end of 1975. Prior to the Tangshan earthquake, the pile foundation was basically finished. In the first stage of con-struction, total length of the workshop was 100 m, width 66 m, and the plan of the foundation is shown in Fig. 11.
Two hundred and ninety-two piles were driven in the turbine workshop, of which 235 were precast RC piles and 57 were poured boring piles. Precast pile cross section was 50 cm×50 cm, with a length of 26.5 m, including two parts: the upper part was 14 m long, and the lower part, 12.5 m. Main reinforcement in the pile shaft was 4 No. 22 + 4 No. 25, and piles were driven by a D2.5 diesel driven hammer. Diameter of the poured pile was 68 cm, with a length of 26.5 m. On the top of the pile, 8 No. 16 bars, 9 m long, were placed uniformly around the top. The pile-supported platform was a square cone. There were: four-pile sup-ported platforms and two-pile supported ones. Total height of the platforms was 1.5 m. There were 84 platforms, and those on E-and F-axis were basically completed; most in D-axis were also completed, but the remaining were under construction.
The foundation soil of the workshop was coastal soft soil and the ground was low and depressed. Elevation of the existing hydraulic fill surface was only +2.03 m, but the design ground surface elevation was +5.40 m, therefore fill was required (Table 13).
b. Earthquake damage
Many ground fissures occurred in the range of the pile foundation, especially those devel-oped along the north coast, the width of which was generally under 10 cm, with a maximum of 20-30 cm.
Displacement and tilting of platforms in detail can be seen in the measurement record (Fig. 11). On the F-axis the absolute values of obvious tilting and displacement in the north-east direction could not be measured, as the datum point had been destroyed. Having selected D-5 platform as a new datum point and the center line between D-5 platform and D-18 platform as a datum line, the relative displacement and relative tilting for each platform were measured. As shown in Fig. 11, displacement of all platforms on F-axis were greater in the north-east direction; maximum displacement in the east direction was up to 1.3 m, while displacements in the north direction were all over 0.5 m. Height differences from tilting of the platforms were usually greater than 10 cm, with a maximum up to 21 cm (near 4°). Plat-
516
forms on D-and E-axis were four-pile supported platforms, and their relative displacements and height differences from tilting were both smaller.
In order to investigate the damage to the pile shaft, excavation was carried out for several typical piles; the depth of excavation was 4 m. After excavation, it was found that pile damage can be divided into three patterns:
1) Many cracks occurred on the pile shaft, passing from the pile top to the depth of exca-vation, with an average width exceeding 2 mm. Concrete in the pile was crushed, and the steel bars exposed. Damage to the pile shaft was serious. For example, 10 penetrating cracks were found at a depth of 2.85 m in excavation for the F-20 platform, with spacing about 30 cm, maximum width up to 10 mm. Concrete in the pile was crushed and fell off (Fig. 12a). Damage to the F-21 platform was similar to F-20 (Fig. 12b).
2) Damage was serious within 1 m from the pile top; damage was less serious below 1 m; basically no cracks were found under 2 m. Such patterns of damage were found mostly on D-and E-axis, as shown in Fig. 12c and 12d.
3) Damage to the pile shaft was slight, and cracks were fine and small in number, e.g., D-5 pile (Fig. 12e). One non-penetrated crack with a width less than 4 mm was discovered within 40 cm from the pile top. However, the poured pile under the D-5 platform fractured at a depth of 1.5 m from the pile top.
It was found in the inspection that the pile foundation deflected after the platform was displaced, and the pile shaft was seriously damaged, as shown in Fig. 13.
Sand boils occurred in the workshop area due to the weak and soft soil, and because the locations of the workshop at the edge of the coast and dock. Many ground fissures occurred near the harbor and the dock. Displacement of the pile-supported platform in the north-east direction was larger, showing the soil mass at the site sliding in that direction. Therefore, it can be concluded that the pile-foundation damage was mainly induced by sliding of soil mass in the earthquake.
3. Conclusion
The above damage investigation shows that the low platform used in the pile-foundation of civil and industrial buildings can achieve a favorable earthquake resistant effect. Such pile foundation obviously reduces the additional settlement due to an earthquake, and mitigates the damage due to soil liquefaction. However, serious damage may also be induced by unproper pile foundation.
(Translator: Lu Rongjian)
517
Table 1. Statistics for the earthquake damage to pile foundation in Tianjin region.
Structure Civil
building (18 nos)
Industrial building (60 nos)
Cold storage (5 nos)
Warehouse (3 nos)
Chimney, water tank and
foundation of equipment etc.
(14 nos)
Total (100 nos)
Damage to the No. 1 2 0 0 4 7 superstructure % 5.6 3.3 0 0 28.6 7 Damage to the No. 0 2 0 1 0 3 pile foundation % 0 3.3 0 33.3 0 3
Remark: one of industrial buildings and one of warehouses had not been built completely.
Table 2. Bearing capacity of single pile (ton-force).
No. of test pileTest type
No. 1 (t.f)
No. 2 (t.f)
Static loading test 32 38
Dynamic test
Initial driving 15.1 21.1
Second driving 35.4 37.0
518
SOME DATA ON THE EARTHQUAKE-SUBSIDENCE OF THE SOFT CLAYEY SOIL FOUNDATION
Weng Lunian,1 Xie Junfei2
The damage due to earthquake-subsidence of soft clayey soil was not significant in past severe earthquakes. Therefore, attention was not paid to it and, consequently, there is little data relating to it. The mechanism of earthquake-subsidence is controversial now. It is uncertain which kind of soil is susceptible to earthquake-subsidence.
In the coastal area of Tianjin the surficial layer is several tens of meters thick and consists of soft clayey soil. During the 1976 Tangshan earthquake, all of the soft clayey soil foundations experienced varying degrees of subsidence.
The vast number of subsidence examples supply valuable data to determine whether soft clayey soil can lead to damage during an earthquake. This data can also be used to find out the condition at which foundation-subsidence of soft clayey soils takes place and to check the estimation techniques of earthquake-subsidence.
1. Data selection of earthquake-subsidence
This section deals with permanent deformation of saturated soft clayey soil foundations under the influence of earthquakes. Such research must select typical soft clayey soil foundations for data-collecting. The following are the prerequisites:
(1) In order to preclude earthquake-subsidence caused by liquefaction of a soil layer, the selected foundation cannot contain fine-silty sand and saturated-low plasticity silt, which is susceptible to liquefaction.
(2) The type of building and its footing must be simple and representative, i.e., it is accepted extensively in Tianjin.
(3) In order to avoid unrepresentative data, a group of buildings must be selected. Only in this way, is the average of any index and measurement value acquired.
(4) The selected buildings must have complete data about the design of their upper structure and geological investigation of their foundations. Specific data needed is: data of geological investigation and routine physical and mechanical tests, data of laboratory triaxial vibration test which simulates the earthquake condition, data of field-vibro-bearing test and
1 Tianjin Engineering Geological Division 2 Institute of Engineering Mechanics SSB
519
subsidence observation before and after Tangshan Earthquake. Finally the design chart of the buildings is needed.
According to the four prerequisites mentioned above, Wang Hailou residential quarter and Jiangang Cun residential quarter of Xingang District, Tianjin were selected. The foundations of 12 residential buildings (3-4 stories) and a school building (3-stories) were chosen to be studied from the two quarters as representative (Fig. 1-4).
2. Data of earthquake-subsidence of typical buildings
The earthquake-subsidence of Wang Hailou and Jiangang Cun residential quarter were studied by field vibro-bearing tests and laboratory triaxial vibration tests.
The laboratory dynamic strength and static strength test was carried out with stress controlled-single sample, stress-controlled-two samples and strain-controlled on the soft clayey soil sampled from Wang Hailou and Jiangang Cun quarter. The results were compared to study the strength variation of the foundation soil (Fig. 5). The limit value of the ratio of dynamic strength to static strength is 0.762.
In order to make clear the characteristic strength and deformation of the soft soil under conditions at which dynamic load and static load were added together, a field vibro-bearing test was carried out in the two quarters. The procedure is to add static load (the extreme loading approximately equal to the weight of the building) first and observe settlement until it is stable. Then, dynamic load is added to observe subsidence. The situation before and after an earthquake is simulated in this way. The results are shown in Figs. 6-8.
In Wang Hailou quarter, No. 3, No. 4, No. 7, No. 15, No. 17 and No. 20 building were selected for study. These buildings were subdivided into A-type and B-type.
No. 3, 4, and 7 buildings are of the B-type with three stories, brick-concrete structure and natural foundation. The raft foundation is embedded to a depth of 0.6 m. The profile and plan of these buildings are shown in Fig. 4. The designed allowable bearing capacity is 5.5T/m2. The total settlement of buildings from the beginning (Dec. 1983)of their construction to July 1978 is 30-40 cm. During the Tangshan earthquake, they subsided 15 cm on average (Fig. 9).
No. 15, 17, and 20 buildings are of A type with 4 stories and natural foundation. The raft foundation is also embedded to 0.6 m. The thickness of the local sand blanket can be 80 cm. The design allowable bearing capacity is 6T/m2. The total settlement of these buildings from their construction (1974) to 1978 is 60-70 cm. They subsided 21.1 cm on average during Tangshan earthquake (Fig. 9).
In Jiamgang Cun quarter, No. 4, 7, 8, 10, 12, 14 building and the school building of Tanggu 7th Middle School were selected for study. They are of 3-storied-brick-concrete structure with reinforced concrete strip-footing. Embedded depth is 1.1 m. Sand blanket was laid locally. The allowable bearing capacity is 5T/m2. The total settlement from the beginning of their construction (Dec. 1972) to 1978 is as much as 60 cm. During Tangshan Earthquake in 1976 the average subsidence is 7.8 cm (Fig. 10) .
520
Subsidence values for every observation point of the 7 buildings, collected before and after the earthquake, are plotted in Fig. 11-17. The heavy lines in the diagrams represent the plan scheme of the buildings. The numerals are the observation points from which differential subsidence of the same building can be recognized.
The subsoil of Wang Hailou building quarter can be divided into three layers. +4-+1 m (Dagu elevation) soft clay; beneath +1.0 m, nearly all mucky loam; beneath-13 m, gradually becoming hard (Table 1). The design allowable bearing capacity is 3T/m2 for the embedded depth of 1.0 m. In the design, however, this value was exceeded.
The subsoil of the Jiangang Cun buildings quarter can be divided into three layers +4.7-+3.0 m (Dagu elevation) filled soil; +3.0-+1.0, clay; below 1.0 mm, mucky clay. The allowable bearing capacity at the level of +3.0 m is 8T/m2 (Table 2).
(Translators: Xie Junfei, Weng Lunian)
521
Tabl
e 1.
Sub
soil
of W
angh
ailo
u re
side
ntia
l qua
rter.
In
dex
of so
il pr
oper
ties
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
u-lu
s of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
Fille
d
1.0
1.0
Plai
n fil
l
gray
, slig
ht w
et
artif
icia
lly fi
lled
soil
dom
inat
ed b
y lo
am w
ith so
me
impu
ritie
s
soil
1.3
2.3
clay
br
owni
sh y
ello
w,
wet
, pla
stic
and
ho
mog
eneo
us c
lay
with
hum
us
35
.5
34.9
17
.9
1.80
1.
07
1.04
91
94
23
.0
19.8
0.
53
0.93
15
0.
28
0.
01
0.05
6
32
35
allu
vial
de
posi
t 1.
0 3.
3 m
uck
y cl
ay
gray
ey b
lack
, sat
u-ra
ted,
flow
ed,
hom
ogen
eous
m
uck
with
man
y or
gani
c m
ater
ial
and
with
out b
ed-
ding
36.8
1.
75
1.13
89
17
.9
1.01
1.
61
0.01
0.
083
24
Lacu
strin
e de
posi
t 10
4.
3
muc
ky
clay
gray
ey b
row
n,
satu
rate
d, fl
owed
, pl
astic
and
hom
o-ge
neou
s muc
ky
clay
with
a li
ttle
hum
us
522
Tabl
e 1.
con
tinue
d.
Subs
oil o
f Wan
ghai
lou
resi
dent
ial q
uarte
r.
Inde
x of
soil
prop
ertie
s
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
u-lu
s of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
0.
7 5.
0 lo
am
gray
ey b
row
n,
satu
rate
d, so
ft,
plas
tic a
nd
hom
ogen
eous
loam
w
ith o
rgan
ic
mat
eria
l
0.3
5.3
cl
ay
gray
ey b
row
n,
satu
rate
d, so
ft,
plas
tic,
hom
ogen
eous
cla
y w
ith o
rgan
ic m
ate-
rial
42.9
1.
67
1.34
88
22
.3
1.00
13
0.19
0.
048
39
shal
low
m
arin
e ac
cum
u-la
tion
1.7
7.0
muc
ky
loam
brow
nish
gra
y,
satu
rate
d, fl
owed
, pl
astic
muc
k, lo
am
with
org
anic
m
ater
ial a
nd a
littl
e fr
agm
ente
d sh
ell
38.5
1.
78
1.12
93
16
.1
1.34
23
0.
05
0.05
7 32
1.0
8.0
m
uck
y cl
ay
brow
nish
gra
y,
satu
rate
d, lo
wed
, pl
astic
muc
ky c
lay
with
a li
ttle
orga
nic
mat
eria
l
44.5
1.
75
1.26
96
18
.81
1.38
19
0.
02
0.10
0 21
0.3
8.3
m
uck
brow
nish
gra
y,
flow
ed, o
rgan
ic
mat
ter-
bear
ing
muc
k 56
.7
1.59
1.
70
91
25.6
1.
41
14
0.01
0.
149
16
523
Tabl
e 1.
con
tinue
d.
Subs
oil o
f Wan
ghai
lou
resi
dent
ial q
uarte
r.
In
dex
of so
il pr
oper
ties
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
u-lu
s of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
0.7
9.0
lo
am
brow
nish
gra
y,
satu
rate
d, p
last
ica-
ble,
hom
ogen
eous
or
gani
c m
atte
r-be
arin
g lo
am
shal
low
m
arin
e
0.3
9.3
m
uck
y cl
ay
brow
nish
gra
y,
satu
rate
d, p
last
ica-
ble,
hom
ogen
eous
or
gani
c m
atte
r-be
arin
g m
ucky
cla
y
4.49
1.
68
1.35
91
19
.1
1.28
16
0.
10
0.06
4 32
accu
mu-
latio
n 0.
4 9.
7 lo
am
brow
nish
gra
y,
satu
rate
d, so
ft,
plas
tic lo
am w
ith
bedd
ing
3.6
13.3
m
uck
brow
nish
gra
y,
satu
rate
d, fl
owed
, ho
mog
eneo
us
muc
k w
ith fr
ag-
men
ted
shel
l and
or
gani
c m
ater
ial
56.7
58
.7
48.9
1.61
1.
54
1.61
1.67
1.
82
1.53
93
88
88
24.6
30
.4
23.9
1.41
1.
10
1.09
15
13
10
0.07
0.
01
0.21
0.18
4 0.
212
0.14
0
14
13
17
524
Tabl
e 1.
con
tinue
d.
Subs
oil o
f Wan
ghai
lou
resi
dent
ial q
uarte
r.
In
dex
of so
il pr
oper
ties
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
ulus
of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
allu
vial
19.3
cl
ay
gray
ey b
row
n gr
ayey
bla
ck p
las-
ticab
le h
omog
e-ne
ous c
lay
with
lo
ess-
doll
and
orga
nic
mat
eria
l
28.3
1.
88
0.86
90
18
.3
0.70
18
0.
14
0.03
9
42
525
Tabl
e 2.
Sub
soil
of Ji
anga
ngcu
n re
side
ntia
l qua
rter.
In
dex
of so
il pr
oper
ties
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
u-lu
s of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
artif
icia
l ac
cum
u-la
tion
2.
3 2.
3 pl
ain
fill
brow
n pl
ain
fill
dom
inat
ed b
y cl
ay
with
littl
e sl
ag o
f fu
rnac
e an
d lim
e an
d hu
mus
33.4
34
.4
1.78
1.
82
1.05
1.
02
87
92
20.4
18
.5
0.57
0.
83
15
18
0.33
0.
15
0.06
3 0.
069
30
27
allu
vial
1.
4 3.
7
muc
ky
clay
brow
n, sa
tura
ted
flow
ed, h
omo-
gene
ous m
assi
ve
muc
ky c
lay
with
iro
n ox
ide
and
hum
us
38.6
1.
82
1.08
98
17
.3
1.17
19
0.
03
0.06
1 30
0.6
4.3
cl
ay
brow
nish
gra
y, so
ft an
d Pl
astic
cla
y w
ith o
rgan
ic m
ate-
rial
37.1
1.
79
1.09
93
18
.7
0.93
5
0.22
0.
082
24
shal
low
m
arin
e ac
cum
u-la
tion
2.7
7.0
lo
am
brow
n, g
ray,
satu
-ra
ted,
soft
and
plas
tic lo
am w
ith a
lit
tle o
rgan
ic m
ate-
rial f
ragm
ente
d sh
ell a
nd b
eddi
ng
stru
ctur
e
26.6
33
.0
1.87
1.
84
0.83
0.
97
87
93
11.3
15
.2
1.26
1.
07
17
18
0.26
0.
19
0.03
3 0.
043
53
40
0.
3 7.
3
muc
ky
clay
gray
ey b
row
n sa
tura
ted
and
flow
ed m
ucky
cla
y
44.5
1.
77
1.23
99
19
.2
1.29
14
0.
12
0.06
9 30
526
Tabl
e 2.
con
tinue
d. S
ubso
il of
Jian
gang
cun
resi
dent
ial q
uarte
r.
Inde
x of
soil
prop
ertie
s
Gen
esis
of
soil
laye
rs
Thic
k-n
ess
(m)
Dep
th
(m)
Soil
type
s D
escr
iptio
n of
so
il la
yer
Wat
er
cont
ent
(%)
Uni
t w
eigh
t (g
/cm
3 )
Voi
d ra
tio
(%)
Deg
ree
of
satu
ra-
tion
(%)
Inde
x of
pl
asti-
city
Inde
x of
liq
ui-
dity
Ang
le
of
inte
r-na
l fr
ic-
tion
Coh
e-si
on
(kg/
cm
2 )
Coe
ffi-
cien
t of
com
pres
-si
bilit
y (c
m2 /
kg)
Mod
u-lu
s of
com
-pr
es-
sibi
lity
(kg
/cm
2 )
4.2
11.5
lo
am
gray
ey b
row
n,
satu
rate
d, so
ft an
d pl
astic
loam
with
fr
agm
ente
d sh
ell
and
orga
nic
mat
e-ria
l and
inte
rca-
late
d w
ith m
icro
-la
yer o
f san
dy
loam
27.9
33
.3
33.4
1.89
1.
83
1.81
0.83
0.
98
1.00
91
92
91
12.5
11
.6
13.7
1.02
1.
78
1.29
27
16
21
0.20
0.
09
0.06
0.03
5 0.
020
0.04
7
49
94
39
shal
low
m
arin
e 0.
3 11
.8
muc
k br
own,
satu
rate
d an
d flo
wed
muc
k 58
.2
1.59
1.
72
93
25.5
1.
31
16
0.10
0.
096
23
accu
mul
atio
n
4.5
16.3
m
uck
y cl
ay
gray
ey b
row
n,
satu
rate
d an
d flo
wed
muc
ky c
lay
with
littl
e hu
mus
, fr
agm
ente
d sh
ell
and
bedd
ing
stru
ctur
e
49.3
40
.8
44.1
1.67
1.
71
1.72
1.45
1.
25
1.29
93
89
93
24.9
19
.1
20.3
1.03
1.
14
1.21
18
12
14
0.06
0.
21
0.13
0.10
2 0.
086
0.07
9
23
23
25
3.4
19.7
cl
ay
gray
ey b
row
n,
satu
rate
d,
plas
ticab
le a
nd
hom
ogen
eous
cla
y w
ith h
umus
and
sh
ell
42.0
37
.0
1.72
1.
83
1.26
1.
05
91
97
23.3
21
.5
0.96
0.
93
17
9 0.
08
0.44
0.
066
0.04
5 30
40
527
Tabl
e 2.
con
tinue
d. S
ubso
il of
Jian
gang
cun
resi
dent
ial q
uarte
r.
allu
vial
20.0
cl
ay
brow
nish
bla
ck,
satu
rate
d, h
ard
and
plas
tic c
lay
with
or
gani
c m
ater
ial
528
Figure 1. Location map of Wanghailou and Jiangangcun quarter.
Figure 2(a). Profile of No. 7.8 building of Jiangangcun quarter (elevation: m).
Figure 2(b). Plane for No. 7.8 building of Jiangangcun quarter (unit: mm).
529
Figure 3. Structure scheme of No. 4 building of Jiangangcun quarter.
Figure 4. Structural scheme of Wanghailou quarter (unit: mm).
Figure 5. Plot of R Rd s/ (dynamic strength/static strength) versus e f (strain).
530
Figure 6. Static and dynamic loading P-S curve (No. 2, 5 buildings of Wanghailou block).
Figure 7. Static and dynamic loading P-S curve (No. 1, 4 buildings of Jiangancun block).
531
Figure 8. Plot of subsidence Sd and acceleration of vibration curve Z(g).
No. 3, subsiding 14.0 cm; No. 7, subsiding 14.4 cm; No. 4, subsiding 17.0 cm; No. 20, Subsiding 15 cm; No. 17, Subsiding 24.0 cm; No. 15, Subsiding 24.4 cm
Figure 9. Subsidence curve of Wanghailou quarter (figures marked on curves are No. of buildings).
532
No. 12, subsiding 5.0 cm; No. 10, subsiding 4.0 cm; No. 7, Middle School, subsiding 5.5 cm; No. 8, subsiding 7.0 cm; No. 7, subsiding 7.0 cm; No. 4, subsiding 11.0 cm; No. 14, subsiding 15 cm.
Figure 10. Subsidence curve of residence buildings, Jiangangcun quarter (figures marked on the curves are no. of buildings).
Figure 11. Subsidence of No. 3 building of Wanghailou quarter (unit: mm).
533
Figure 12. Subsidence of No. 4 building of Wanghailou quarter (unit: mm).
Figure 13. Subsidence of No. 5 building of Wanghailou quarter (unit: mm).
Figure 14. Subsidence of No. 21 building of Wanghailou quarter (unit: mm).
534
Figure 15. Subsidence of No. 24 building of Wanghailou quarter (unit: mm).
Figure 16. Subsidence of No. 14 building of Wanghailou quarter (unit: mm).
Figure 17. Subsidence of No. 10 building of Wanghailou quarter (unit: mm).
535
LIQUEFACTION DATA OF SANDY SOIL WITH A SMALL AMOUNT OF CLAY GRAINS IN TIANJIN
Weng Lunian,1 Shi Zhaoji2
During the Tangshan earthquake on 28 July 1976, the sandy soil, containing small amounts of clay grains, in Tianjin had a variety of responses. In some places large areas of soil were liquefied, and water and/or sand erupted or gently vent-erupted to surface; in other places nothing happened at all. Based on the macroscopic field damage data and liquefaction analysis of the sandy soil after the earthquake, the authors consider that liquefaction potential is closely related to the genetic type, formation age, density and composition of clay grains.
The liquefaction zone is defined by macroscopic field data after the earthquake (including the main earthquake and multiple aftershocks) as areas where water and/or sand were erupted. Otherwise it is defined as unliquefied zone.
1. Influence of Generic Type and Formation Age on Liquefaction
Generic type and formation age are two important factors influencing the liquefaction potential of sandy soil with small amounts of clay grains. The liquefied zones are generally located in the old river bed and in the old valley flat of the present river. The most extensive development of surficial crack and eruption of water and sand occurred at the Tianjin Woolen Mill, Medium Plate Factory in Liulin; No. 42 Middle School, Orthopedics Hospital in Bai Tangkou; the highway from Tianjin to Baxian county, etc., which are all located in the old beds of the Haihe River and the Daqinghe River. These soil zones are about 100-year old modern deposits and are saturated and soft. In the zones where no macroscopic surficial crack and eruption or vent-eruption can be seen, the sandy soil with little clay grains were formed generally 3000 years ago. It is marine deposit, aged and condensed. The same marine deposit of young age in the areas along the coastline is soft, and allowed eruption of water and sand or vent-eruption in large areas during the Tangshan earthquake.
2. Influence of Physical Properties and Composition of Grains on Liquefaction
After the earthquake the liquefied and unliquefied sandy soils containing small amounts of clay grains are not different in their physical or mechanical properties (Table 1), but differ in their composition of grains (Table 2). In the liquefied sandy soil, clay grains are in low content, silt grains in high content, and the coefficient of uniformity is low. In the unliquefied sandy soil, clay grains are in high content, silt grains in low content, and coefficient of uniformity is high. 1 Tianjin Engineering Geological Division 2 Institute of Engineering Mechanics, SSB
536
3. Change of the Soil Property Before and After Earthquake
Before and after the earthquake, no apparent change is shown in the physical index of the sandy soils except for angle of internal friction and modulus of compressibility. This indicates that no matter how the sandy soils are liquefied they tend to compact under the influence of earthquakes (Table 3).
4. Change of the SPT Before and After Earthquake in Liquefied Zone
By experiment, the SPT blow count of the sandy soil after an earthquake is generally one blow more than that of the soil before the earthquake (Table 4).
5. Difference of SPT Blow Count in Liquefied and Unliquefied Zones
Statistics and analytical results of SPT show apparent difference for the liquefied and unliquefied zones (Table 5).
(Translator: Shi Zhaoji, Weng Lunian)
Table 1. Physical index of liquefied and unliquefied zone (by Tianjin Engineering Geological Division).
Physical Liquefied zone Unliquefied zone
index Statistical average
Standard deviation
Number statistical
Statistical average
Standard deviation
Number statistical
Water content(%) 27.3 ±2.2 56 27.3 ±2.0 44 Wet unit weight (g/cm3) 1.87 ±0.03 56 1.87 ±0.04 44 Dry unit weight (g/cm3) 1.48 ±0.04 55 1.46 ±0.05 41
Void ratio 0.84 ±0.05 56 0.86 ±0.05 44 Degree of saturation(%) 88.4 ±3.6 56 88.3 ±2.5 44
Liquid limit(%) 29.1 ±1.9 56 29.3 ±2.8 12 Index of plasticity (%) 77 ±1.6 56 81 ±1.6 10 Index of liquidity(%) 0.67 ±0.086 55 0.83 ±0.37 42
Angle of internal friction 30° ±4° 48 33° ±5° 37 Cohesion (kg/cm2) 0.14 ±0.10 48 0.22 ±0.09 37
Coefficient of compressibility (cm2/kg) 0.016 ±0.006 50 0.012 ±0.004 40
Modules of compressibility (kg/cm2) 125 ±4.2 49 123 ±31 41
537
Tabl
e 2.
The
par
ticle
ass
ocia
tion
of li
quef
ied
and
unliq
uefie
d zo
ne.
Pa
rticl
e as
soci
atio
n ( %
)
Del
imita
tion
0.25
-0.1
mm
0.
10-0
.05
mm
0.
05-0
.005
mm
<.
0.00
5 m
m
coef
ficie
nt o
f un
iform
ity
of z
one
Stat
. av
g.
Stan
d. d
ev.
Stat
. nu
m.
Stat
. av
g.
Stan
d. d
ev.
Stat
. nu
m.
Stat
. av
g.
Stan
d. d
ev.
Stat
. nu
m.
Stat
. av
g.
Stan
d. d
ev.
Stat
. nu
m.
Stat
. av
g.
Stan
d. d
ev.
Stat
. nu
m.
lique
fied
zone
1)
unliq
uefie
d zo
ne2)
liq
uefie
d zo
ne1)
un
lique
fied
zone
2)
5.4
2.4
9.1
4.7
±5
±1.8
±9
±1
4.1
43
44
17
52
60.6
68
.2
46.8
56
.2
±13.
1 ±9
.9
±15.
4 ±1
3.5
54
45
20
68
31.3
25
.8
32.8
31
.5
±13.
7 ±9
.9
±18.
4 ±1
5.2
54
44
25
68
5.1
6.0 6 9
±2.9
±2
.7
±1.4
±1
.4
±3.8
53
45
21
66
3.8
3.3
2.8
5.7
±2.5
±2
.3
±0.8
±4
.2
53
44
16
46
1)
By
Tian
jin E
ngin
eerin
g G
eolo
gica
l Div
isio
n
2) B
y G
ener
al S
urve
y C
o., D
ept.
Of M
etal
lurg
ical
Indu
stry
538
Ta
ble
3. P
hysi
cal i
ndex
bef
ore
and
afte
r the
ear
thqu
ake.
(b
y Ti
anjin
Eng
inee
ring
Geo
logi
cal D
ivis
ion
and
Surv
ey C
o., D
ept.
of N
o. 1
Mac
hine
ry In
dust
ry)
Li
quef
ied
zone
U
nliq
uefie
d z
one
Phys
ical
B
efor
e ea
rthqu
ake
Afte
r ear
thqu
ake
Bef
ore
earth
quak
e A
fter e
arth
quak
e
inde
x st
atis
tical
av
erag
e st
anda
rd
devi
atio
n st
atis
tical
nu
mbe
r st
atis
tical
av
erag
e st
anda
rd
devi
atio
n st
atis
tical
nu
mbe
r st
atis
tical
av
erag
e st
anda
rd
devi
atio
n st
atis
tical
nu
mbe
r st
atis
tical
av
erag
e st
anda
rd
devi
atio
n st
atis
tical
nu
mbe
r W
ater
co
nten
t (%
) 28
.6
±4.2
29
28
.6
±4.5
14
9 28
.5
±3.6
54
28
.4
±3.4
10
0
Wet
uni
t w
eigh
t (g
/cm
3 )
1.92
±0
.06
38
1.93
±0
.06
153
1.91
±0
.06
67
1.92
±0
.06
91
Voi
d ra
tio
0.82
±0
.096
29
0.
80
±0.0
83
136
0.81
±0
.011
51
0.
82
±0.0
82
84
Inde
x of
pl
astic
ity
(%)
7.7
±1.9
1 29
7.
6 ±1
.65
167
7.8
±1.6
9 57
7.
4 ±1
.94
104
Inde
x of
liq
uidi
ty(
%)
1.06
±0
.47
26
1.18
±0
.49
155
1.35
±0
.57
57
1.21
±0
.52
110
Ang
le o
f in
tern
al
fric
tion
25.5
° ±4
8
32°
±6
18
26°
±6
8 32
±2
19
Coh
esio
n (k
g/cm
2 )
0.15
±0
.08
8 0.
14
±0.0
7 18
0.
14
±0.0
7 8
0.14
2 ±0
.085
19
Coe
ff. o
f co
mpr
es-
sibi
lity
(cm
2 /kg
)
0.02
±0
.01
19
0.01
8 ±0
.013
60
0.
025
±0.0
13
63
0.02
±0
.01
36
Mod
ules
of
com
pres
-si
bilit
y (k
g /c
m2 )
10
3.6
±56
57
80.5
±5
6.5
28
96.9
±5
1.6
28
539
Table 4. N, SPT blow count before and after the earthquake.
Test site Time Depth of SPT Blow count Statistical number
Engineering Machine plant, Tianjin
Before the quake
4.0-5.0 5.0-6.0 6.0-7.0 7.0-8.0 8.0-9.0 9.0-10.0
1.6 3.6 5.2 6.6 9.7 6.0
32 (by Survey Co., Dept. of No. 1 Machinery Industry)
No. 1 Machine Tools Plant, Tianjin
After the quake
4.0-5.0 5.0-6.0 6.0-7.0 7.0-8.0 8.0-9.0 9.0-10.0
2.6 4.3 8.8 5.6 7.9 6.0
34 (by survey Co., Dept. of No. 1 Machinery Industry, Tianjin Engineering Geological Division)
Note: The N, SPT blow count is average at the depth
Table 5. N, SPT blow count of liquefied and unliquefied zone (by Tianjin Engineering Geological Division).
Delimitation of zone SPT Blow count
statistical average standard deviation statistical number
liquefied zone unliquefied zone
9 15
±4.2 ±6.0
54 45
540
SOIL LIQUEFACTION AT LUTAI DISTRICT DURING TANGSHAN EARTHQUAKE
Zhou Shengen,1 Academy of Railway Science2
1. Introduction
Located in the southwest part of Tangshan city, Lutai district is 48 km from the epicenter of the Tangshan earthquake of M=7.8. However, this district, being seriously damaged, is an intensity anomaly of IX in the area of intensity of VIII. From the statistics of Ninghe county government, 87% of the industrial and civil buildings were heavily damaged; some com-pletely collapsed. Subsoil liquefaction was one of the main factors causing such tremendous losses.
Sand boils induced large scale ground surface settlement at the center of Lutai district. In fact, one quarter of 43,333 hectares of farmland was covered with sand boils in Ninghe county and part of the railway was inundated. Soil liquefaction led to fractures of, and set-tlements to, many industrial and civil structures. Along the 280 km embankment of Ji canal, 70 km were destroyed within the area of Ninghe county, with subsidence occurring at 35 places. The foundation near the Lutai highway bridge sank 1.7-2 m, 69 places along the embankment failed due to differential settlement, and landslides occurred at 15 places due to subsoil instability.
Of the 2600 tube wells in the Ninghe area, 1410 were destroyed by the earthquake, 1020 of which cannot be recovered. Well tube bursting and gushing, sand boils flowing into the well, and floor heaving in pump houses were very common.
Generally speaking, where sand boils occurred on a large scale, damage was higher. In Lutai district, most of the farm machinery factories, storehouses and grain depots must be rebuilt. In the chemical fertilizer plant, which is 300 m from a farm machinery factory, there were no sand boils at the surface, only in a tube well; both the factory and administration buildings did not collapse, and floor cracks occurred in only simple structures. Earthquake hazard was comparatively low there.
From November 1976 to May 1977, surveying of Lutai soil and geotechnical investiga-tion of its liquefaction were carried out by the Hubei Institute of General survey, the Third Design Institute of Ministry of Railway and the Academy of Railway sciences, Ministry of Railway, et al.
1 Academy of Railway Science 2 General Survey Institute, HuBei
541
2. General situation of sand boil at Lutai district
Sand boils took place mainly in the eastern and the center sections of Lutai town (i.e., area A surrounded with a dashed line in Fig. 1). According to statistics, there were roughly 300 places where sand boils occurred. Sand boils did not exist, or occurred in lesser amounts in other areas (titled as area B). The boiling material is gray sandy loam. Table 1 and Fig. 2 show the results of granularmetric analysis for 9 sandy samples. The comprehensive results of liquid and plastic limit tests are summarized in Table 2 for 16 sand boil samples with aver-age grain diameter 0.056-0.08 mm, coefficient of uniformity 1.5-6.2 and plastic index 4.8-8.2. The soil should be classified as sandy loam according to the Chinese Code (Natural Foundation Standard of Industrial and Civil Construction). The water salt content reaches 10%.
Two features of sand boils in Lutai district can be summarized as follows:
(1) Large sand boils—the sand mound at each hole is 1-10 m3 in general, with some reaching 20-40 m3. The boiling tapes of them vary a lot, ribbon, flake, or cluster.
(2) Long duration flowing time. Four cases are divided as follow:
(a) Sand boils stopped flowing at 10-30 days after the earthquake on July 28.
(b) Begins again and flows for 10-15 days due to the after shock on Nov. 15 (M=6.9)
(c) Water flow began on July 28 and did not stop until November 15.
(d) There were 12 places where water flow didn't stop from the beginning of July 28 until January 24. The places are located in the northeast of Lutai town.
3. Conditions of engineering geology
Lutai town is situated on a coastal plain. Ji canal, in the northwest section of the town, flows from the northeast to the southwest and into the Bohai sea. The topography is even and there are many rivers and lakes in the town. Ground elevation is generally 2-3 meters, but in the old town, the elevation is 3-5 meters.
Bedrock is Tertiary Conglomerate, which is covered by Quaternary sediment, thickness of which is 500-600 m. The sediments consist of alluvial diluvial cohesive soil, mucky cohe-sive soil, and sandy loam due to the deposition actions both of the Ji canal and Bohai sea. Referring to the information given by the Institute of Geology, Academy of China, about 2000 years ago the coastline was very near Lutai town. This proves that the deposit history of the upper strata is shorter, thus the soil is soft with low strength and high compressibility.
The groundwater level, which changes with seasons, in this district is high, generally 0.5-1 meter. Because of sea water intrusion, periodically the water contains alkali and is not drinkable.
The subsoil can be divided into 4 layers on the basis of investigation.
542
(1) back fill-partially distributed. Its thickness is 1.5-4.5 m and properties vary due to the difference of deposition period and contents. Generally the back fill is loose or of low den-sity.
(2) recent cohesive soil formed by alluvium and diluvium is 1.5-4.5 m thick with plastic or soft plastic properties. Iron, manganese oxidizer, mica disc are contained in small amounts.
(3) dark gray mucky cohesive soil and sandy loam interbedding layer is 21-22 m thick with soft plastic or liquid plastic properties. The soil contains mica, white shell, and silty sand with a bit of smell.
(4) older dark brown loam formed by alluvium and diluvium is less than 22 m thick. Silty sand is interbedded in the central area and is saturated with medium density.
The subsoil can be further divided into 9 layers. The properties and physical indexes of each are shown in Table 3. Fig. 3 is a geological profile from east to west (I-I') and shows that the sequence of the layer is stable.
4. Liquefied layer
From analysis of soil properties, the sandy loam of layer III-I and V can be liquefied. Layer III-I is dark gray saturated sandy loam and intercalation of the III layer. It appears with lens shape distributing extensively in the northeast of Lutai town (Fig. 1). The top of the layer lies 5.5 m deep and is 0.5-1 m thick.
The results of grain-size analysis are listed in Table 4 and a distribution curve is presented in Fig. 4. It can be seen from the comparison between Fig. 2 and Fig. 4 that the results of grain-size analysis is basically consistent with layer III-I and sand boil sample.
In addition, Fig. 4 indicates that the range of sand boils is basically consistent with the distributed range of layer III-I. Where there is III-I, the occurrence of sand boils is more serious, And thus, it is enough to prove that the soil had been liquefied during an earthquake.
Layer V is composed of saturated dark sandy loam with plastic or soft plastic properties. The top of the layer lies 10-11 m deep and is 2.5 m thick. The results of grain-size analysis and plastic and liquid limit are listed respectively in Tables 5 and 6. The range of the grain-size distribution curve is presented in Fig. 5.
It can be found from Fig. 1 that sand boils are also present at some places where there is a lens of layer III-I. This was very serious near the agriculture machinery office in town. Whereas the granulometric composition of sand in those sites is quite consistent with that of layer V, the clay content is decreased (Fig. 2 comparing to Fig. 5).
Fig. 6 shows the comparison of the sand boil samples with layer V of a borehole. How-ever, near the borehole, there is no layer III-I, it seems that both grain-size distribution curves are consistent.
543
Fig. 7 (a) shows the correlation of the embedded depth of layer V versus specific penetra-tion resistance, where there is layer III-I. Fig. 7(b) shows also the correlation in the whole district. It demonstrates that sandy loam of layer V has large specific penetration resistance where sand boils did not take place.
Layer VI is mucky loam, intercalated sandy loam and is rather thick. The intercalary layer is unstable and changeable in specific penetration resistance. This is mainly due to a big change of sand content in sandy loam. It is very difficult to identify whether liquefaction takes place during an earthquake.
Layer VII is a dark clay formed by alluvium and diluvium. In the center of the town, layer VII is intercalated by thick silt sand. The results of grain-size analysis for this layer are listed in Table 7. The grain-size distribution curve is plotted in Fig. 8. Average grain-size is between 0.13-0.16 mm. The composition of layer VII differs a lot from that of sand boil materials.
5. In situ testing of liquefied layer and its results
A static cone penetration test is mainly used for in-situ testing. Standard penetration test is only applied to sandy loam of layer III-I, V and silt of VII in part boreholes. Fig. 1 illus-trates the layout of the borehole.
The static cone penetration test used a single-bridge probe; the area of transection is 15 or 16 square centimeters. The standard penetration test is conducted by way of casing protect-ing borehole wall, machinery elevating, releasing falling hammer, slurry circulatory drilling, clean-out hole, free hammer.
(1) Results of static cone penetration test
Fig. 9 shows the test curves of static cone penetration tests for 4 boreholes in section II-II' of Fig. 1. It can be found that the thickness of stratum III-I is smaller, mostly at 0.5-1.0 m. As a result of the influence of upper and lower soft layers, specific penetration resistance curves are triangally distributed with change in peak values and very unstable, roughly between 30 and 130 kgf/cm.
The thickness of sandy loam in layer V is 2-2.5 m, and the specific penetration resistance is rather stable. The averages are listed in Fig. 8. Fig. 10 is the frequency number. If inspection is made for the two sets of data, the inspected consequence will show that the difference between them is visible.
The increase of fine grain content, especially the clay grain below 0.05 mm, will intensify liquefaction in sandy loam, but will cause a decrease of specific penetration resistance at the same time. Due to the limited testing data, the direct correlation between them is not yet known. But from the correlation between specific penetration resistance and liquid limit of the soil (Fig. 11), the influence can be observed indirectly because the correlation between liquid limit and clay content is close.
544
(2) Results of standard penetration test
The scatter diagram of hammer blow count for standard penetration tests in sandy loam of layer III-I and V is plotted in Fig. 12, which indicates that the results of tests are more scattered. The blow count of SPT in the area of liquefied soil (area A) is less than that in the unliquefied area (area B). The average blow counts of both areas are 5.4 and 6.5 respectively.
Table 9-12 summarizes the results in 4 investigated places. The results of SPT in deep layer are also shown in the tables.
Conclusions
The liquefied sandy loam in the Lutai district has high clay grain content (average 13.9%) and exceeds the general limit for soil liquefaction. Therefore, the identification of liquefaction limit of sandy loam should be thoroughly evaluated in combination with the soil properties, grain content and granulometric composition; especially the fine grain content, besides the groundwater level, layer depth and SPT / CPT resistance.
(Translators: Ding Xiaoxue, Luo Mingjiu)
545
Table 1. Results of grain-size analysis tests of boiling materials.
Places Grain size (mm)
0.5-0.25 0.25-0.1 0.1-0.05 0.05-0.01 0.01-0.005 <0.005 Storehouse of machine-tooled well
3 57 31 1 8
Outer enclosing wall of grain depot
6 64 22 1 7
Outer enclosing wall of oil storehouse
59 33 1 7
South of highway bridge
11 75 8 1 5
West of dig well office 4 68 22 1 5
Cement plant 17.2 54.1 23.1 1.2 4.2
Side of water well of farm machinery factory
32 42 16.5 1.5 4
The center of farm machinery factory
6 60 29 1 4
In front of the aquatic product company
11 61 22 0 6
Table 2. Results of liquid and plastic limit tests of sand boil samples.
Liquid and plastic limit Liquid limit (%)
Plastic limit (%)
Plasticity index (%)
Maximum 28.9 22.6 8.2
Minimum 23.9 18.4 4.8
Average 26.3 20.4 5.9
Mean square error 1.48 1.17 1.03
546
Ta
ble
3. P
rope
rties
of f
ound
atio
n so
il in
Lut
ai to
wn.
Sequ
enc
e
Ti
ne a
nd
Wat
er
Uni
t Sp
ecifi
c V
oi d D
egre
e of
Li
qui
d Pl
astic
Pl
as-
Liqu
i-
Coh
esio
nal
Fric
- C
ompr
essi
on fa
ctor
of l
ayer
So
il ca
use
of
form
atio
n co
nten
t (%
) w
eigh
t (g
/cm
3 )
grav
ity
g/cm
3 )
ratio
sa
tura
-tio
n lim
it (%
) lim
it (%
) tic
ity
inde x
ditu
in
dex
degr
ee(k
g.f /
cm2 )
tio
n an
gle
1-2
(cm
2 /kg
f)
1-3
(cm
2 /kg
f)
i I
Bac
k fil
l Kc
II
-1
Loam
Qal
pl4-
33
.4
1.91
2.
72
0.86
97
31
.2
18.7
12
.5
0.96
0.
24
16
0.03
1 0.
026
ii II
-2
Loam
Qal
pl4-
35
.1
1.85
2.
72
0.99
97
32
.5
17.9
14
.6
1.19
0.
16
16
0.03
7 0.
032
II
I M
ucky
lo
am
Qm
33
.5
1.88
2.
71
0.93
97
30
.0
17.4
12
.6
1.24
0.
14
21
0.04
4 0.
036
II
I- 1 Sa
ndy
loam
Qm
31
.6
1.95
2.
72
0.85
10
0 25
.6
18.6
7.
0 1.
41
iii
IV
Muc
ky
loam
Qm
38
.3
1.82
2.
72
1.07
97
33
.4
18.9
14
.5
1.33
0.
067
0.05
V
Sa
ndy
loam
Qm
21
.3
2.02
2.
69
0.62
94
24
.3
17.0
7.
4 0.
58
0.01
6 0.
014
V
I M
ucky
lo
am
inte
r-po
late
d sa
nd
loam
Qm
28
.6
1.94
2.
73
0.81
97
34
.8
18.2
16
.6
0.71
0.
3 14
0.
033
0.02
7
iv
VII
Lo
am
Qal
pl-
25
.4
1.99
2.
72
0.72
96
31
.6
16.4
15
.2
0.59
0.
22
21
0.01
1 0.
010
547
Tabl
e 4.
Tes
t res
ults
of s
ampl
e in
laye
r III
-I
Wat
er
Uni
t
Liqu
id
Plas
tic
Gra
nulo
-met
ric c
ompo
sitio
n (%
) co
nten
t (%
) w
eigh
t (g
/cm
3 ) V
oid
Rat
io
limit
(%)
limit
(%)
Plas
ticity
in
dex
Liqu
idit
y in
dex
0.25
-0.1
0.
1-0.
05
0.05
-0.0
1 0.
01-0
.005
<0
.005
33.8
1.
95
0.85
25
.1
18.7
6.
4 1.
36
18.0
47
.5
22.5
3.
0 9.
0
548
Table 5. Results of grain-size analysis test for sandy loam in layer V.
Sample Granulometric composition
number 0.5-0.25 (mm)
0.25-0.1 (mm)
0.1-0.05 (mm)
0.05-0.01 (mm)
0.01-0.005 (mm)
<0.005 (mm)
1 32.0 28.0 19.5 4.5 16 2 20.0 50.0 15.0 4.0 11 3 0.2 5.0 68.8 6 3 17 4 0.4 2.7 71.9 6 3.4 15.6 5 1.0 3.0 20.3 56.9 4.8 14 6 0.1 0.2 25.7 50 4.5 19.5 7 0.3 1.8 70.2 7.5 3.8 16.4 8 2.5 28.5 39.0 17.0 1 12 9 1.8 32.2 42.4 8.5 4.2 10.9 10 33.7 43.1 3.2 5.4 14.6 11 19.5 54.2 9.3 13.0 4.0 12 28.1 47.7 5.2 4.6 14.4 13 31.9 43.6 7.1 2.6 14.8
549
Table 6. Results of liquid and plastic limit for sandy loam in layer V.
Sample number
Sampling depth (m)
Water content
(%)
Liquid limit (%)
Plastic limit (%)
Plasticity index
Liquidity index
1 11.8-12.0 23.5 22.7 14.6 8.1 1.10 2 12.8-13.0 21.4 22.5 14.2 8.3 0.87 3 11.15-11.45 25.6 19.9 5.7 4 12.7-12.9 25.1 20.2 4.9 5 11.4-12.4 24.7 20.0 4.7 6 12.5-12.95 25.4 20.9 4.5 7 11.0 22.6 24.0 17.9 6.1 8 12.5 22.0 18.0 4.2 9 12.5-12.6 22.7 25.3 17.5 7.8 10 10.95 22.4 23.7 15.5 8.2 0.84 11 10.7-11.0 22.5 17.8 5.7 12 12.7-12.9 27.7 19.5 8.2 13 10.6-11.0 23.6 17.0 6.6 14 11.5-12.0 24.8 19.6 5.2 15 12.5-12.8 28.5 19.1 9.4 16 12.2-12.4 21.2 23.0 17.9 5.1 0.65 17 11.6-11.75 20.3 23.2 18.2 5.0 0.42 18 12.5-12.65 22.2 16.4 5.8 19 12.5-12.7 23.3 23.8 17.3 6.5 0.92 20 10.4-10.6 21.7 22.7 18.8 3.9 0.64 21 11.2-11.4 21.9 26.4 16.5 9.9 0.5 22 12.0-12.2 20.8 25.2 15.5 9.7 0.5 23 13.0-13.2 21.2 25.0 15.5 9.5 0.6 24 12.6-12.8 21.5 24.5 15.5 9.0 0.7 25 12.5-12.7 23.0 24.2 15.0 9.2 0.9 26 11.7-11.9 22.4 26.3 16.5 9.8 0.6 27 12.0-12.2 23.8 24.5 15.5 9.0 0.9 28 11.5-11.7 23.0 24.1 15.0 9.1 0.9 29 12.0-12.2 24.2 25.6 16.5 9.1 0.8 30 11.0-11.2 23.3 23.4 14.5 8.9 1.0 31 11.0-11.3 23.7 24.4 15.0 9.4 0.9 32 11.5-11.8 20.8 22.7 14.5 8.7 0.8 33 12.0-12.3 21.4 23.2 14.5 8.7 0.8 Average 24.3 17.0 7.4
550
Table 7. Results of grain-size analysis test of layer VII.
Sampling Grain size (mm)
Sample number
depth (m)
2-0.5 0.5-0.25 0.25-0.1 < 0.1 0.1-0.05
1 22.1 71.5 28.5 2 24.1 6.2 72.9 11.3 3 21.2 3.2 64.8 32.0 4 23.0 0.1 1.4 88.6 9.8 5 23.0 1.4 85.6 11.8 6 24.5 0.6 84.8 14.5 12.6 7 23.0 0.1 10.8 80.9 8.2
Ta
ble
8. R
esul
ts o
f sta
tic c
one
pene
tratio
n te
st o
f san
dy lo
am fo
r lay
er V
.
Liqu
efac
tion
regi
on
No
lique
fact
ion
regi
on
Nos
.
Dep
th o
f st
ratu
m
surf
ace
(m)
Spec
ific
pene
tratio
n re
sist
ance
P s
(kg.
f/cm
2 )
Nos
.
Dep
th o
f st
ratu
m
surf
ace
(m)
Spec
ific
pene
tratio
n re
sist
ance
P s
(kg.
f/cm
2 )
Nos
.
Dep
th o
f st
ratu
m
surf
ace
(m)
Spec
ific
pene
tratio
n re
sist
ance
P s
(kg.
f/cm
2 )
Nos
.
Dep
th o
f st
ratu
m
surf
ace
(m)
Spec
ific
pene
tratio
n re
sist
ance
P s
(kg.
f/cm
2 )
1 10
.7
35.2
10
10
.7
32.9
1
11.1
50
.9
15
11.1
43
.8
2 11
.8
37.5
11
11
.3
37.0
2
10.7
43
.4
16
11.3
49
.6
3 11
.5
41.8
12
10
.1
36.6
3
11.2
59
.0
17
11.2
39
.4
4 10
.9
39.6
13
10
.3
33.3
4
11.2
41
.9
18
11.2
40
.6
5 9.
9 38
.3
14
11.1
40
.5
5 11
.3
36.5
19
10
.6
41.8
6
10.2
37
.0
15
11.6
41
.4
6 11
.2
41.0
20
10
.8
41.8
7
11.2
38
.5
16
10.5
38
.6
7 11
.3
41.9
21
10
.6
38.1
8
11.3
29
.9
17
10.3
39
.6
8 11
.7
44.0
22
11
.0
42.7
9
10.0
43
.0
18
10.2
39
.8
9 11
.5
43.9
23
11
.5
44.4
10
11
.2
42.9
24
11
.1
40.8
11
11
.2
48.7
25
11
.1
39.9
12
11
.2
39.8
26
10
.5
31.9
13
10
.2
51.7
27
10
.5
48.4
14
10
.4
40.2
A
vera
ge
10.7
0 37
.8
A
vera
ge
11.0
3 43
.3
M
ean
squa
re
erro
r 0.
58
3.26
Mea
n sq
uare
er
ror
0.36
5.
28
551
552
Table 9. Test results (Lutai chemical fertilizer factory, groundwater level: 0.4 m, unliquefied, August 1977)
Sampling test In situ test
Type of soil Depth
(m)
Water content w
Plasticity index I p
Unit weight g
Standard penetration
test
Standard cone penetration test
Blow count Artificial fill Loam 2.90 25.7 12.0 1.85 6.45 33.80 6.40 1.95 Sandy loam 8.00 10.70 Mucky loam 9.35 37.30 13.30 1.83 10.60 16.00 11.90 23.5 8.1 2.07 Sandy loam 12.90 21.40 Mucky loam 14.90 30.4 9.6 1.93 16.0 34.70 16.80 1.89 Loam
553
Table 10. Test results (Lutai farm machinery factory, groundwater level: 0.21 m, liquefied, August 1977)
Sampling test In situ test
Type of soil Depth
(m)
Water content w
Plasticity index I p
Unit weight g
Standard penetration
test
Standard cone penetration test
Blow count Artificial fill Loam 3.50 39.30 15.00 1.81 Mucky
Loam 5.00 29.40 12.40 1.89
Sandy loam 6.20 5.0 Mucky loam 9.10 39.40 15.7 1.78 Sandy loam 11.30 5.72 12.40 4.70 12.80 18.50 4.85 2.09 Mucky loam 17.70 21.80 11.90 2.02 Silt
554
Table 11. Test results (Lutai company of aquatic product, groundwater level: 0.43 m liquefied, August 1977)
Sampling test In situ test
Type of soil Depth
(m)
Water content w
Plasticity index I p
Unit weight g
Standard penetration
test
Standard cone penetration test
Blow count Loam 3.00 37.60 14.70 1.85 Mucky
Loam
11.00 22.60 6.10 1.96 Sandy loam 12.54 22.70 4.20 2.0 Mucky loam 17.80 25.50 2.20 1.97 19.75 24.30 6.20 2.0 Silt
555
Table 12. Test results (Lutai printing house, groundwater level: 0.77 m unliquefied, August 1977)
Sampling test In situ test
Type of soil Depth
(m)
Water content w
Plasticity index I p
Unit weight g
Standard penetration
test
Standard cone penetration test
Blow count Loam Mucky
Loam
6.80 12.8 11.05 22.4 8.2 1.95 Sandy loam 11.75 5.2 12.80 8.2 Mucky loam intercalated sandy loam 15.7 31.7 10.6 1.86 Loam
556
Figure 1. The distribution of sand boils.
557
Figure 2. Grain-size distribution curves of sand boil samples.
1. Miscellaneous fill; 2. loam; 3. mucky loam; 4. sandy loam
Figure 3. Geological profile from east to west (I-I' section in Figure 1).
Figure 4. Grain-size distribution curve of sandy loam for layer III-I.
558
Figure 5. Grain-size distribution curve of sandy loam for layer V.
Figure 6. Comparison of sample in layer V and sand boil sample (Cement Plant).
559
Figure 7. Embedded depth of stratum V, specific
penetration resistance versus sand boil.
Figure 8. The range of grain-size distribution curve of sand for layer VII
560
Figure 9. Section II-II'.
(a) Frequency number of specific penetration resistance (ni ) (b) Probabilistic density (f i )curves
Figure 10. Static cone penetration test in sand loam for layer V.
561
Figure 11. Correlation of liquid limit wL versus specific penetration resistance Ps in layer V.
Figure 12. Results of SPT in layer III-I and V.
562
LIQUEFACTION DATA OF THE SATURATED SILT UNDERLYING TIANJIN PETROLEUM CHEMICAL PLANT
Zhang Yuanyi,1 Shi Zhaoji2
1. Engineering Geological condition
(1) Geographic Location and Geological History
The Tianjin Petroleum Chemical Plant is situated on the southern outskirts of Tianjin, between Shang Gulin and Wanjia Matou, 45 km to the urban section of Tianjin city, 10 km to Bohai bay in the east, 110 km to Tangshan city in northeast (Fig. 1).
According to the recorded history for land formation of the west coastline of Bohai Bay, there was a shell embankment on the west side of the plant from Zhangguizhuang-Jugez-huang-Wanjia Matou-Shajingzi to Miaozhuang. The shell embankment near Jugezhuang is 3400 ±115 years old determined by C14. In the east side of the site, there was another shell embankment from Baishaling-Junliangcheng-Nigu-Shanggulin-Mapengkou-Wuditai to Xili-uzhuang. The shell embankment at Shanggulin is 2900 ±120 years old determined by C14 (Fig. 2). Therefore, it is postulated that 2500 years ago the site was part of Bohai Bay. Because river systems of Huanghe and Hai rivers flow into Bohai Bay, large amounts of sandy and muddy materials were deposited there. Gradually the marine and continental soil layers were formed in the top stratum of the site. In the bottom stratum, the soil layers, which were exposed to transgression and continental subsidence several times, show alternative cycles of marine and continental deposit in the section.
(2) Outline of Soil Layers, Topography and Geomorphology
The site is located in the Banqiao Depression (sub-scale tectonic unit) on the east side of Changdong Fracture (compressional, compressional-tortional fracture). Tertiary and Quater-nary sediment (over 1000 m) were laid on the bed rock. Geomorphologically the site belongs to the coastal plain. It is 400 m long from east to west and 1500 m wide south to north. The ground level is generally 3.6-4.0 m (Dagu level ), with smooth relief for the extent of the site. The stratum in the site, to a depth of 40 m, is composed of lst continental alluvial deposit (Q ala
4 ), 2nd marine deposit(Q mb4 ), 3rd continental deposit (Q alc4 ) and 4th marine deposit (Q md4 ).
1 Tianjin Survey Division 2 Institute of Engineering Mechanics, State Seismological Bureau
563
Location of the representative borehole for individual factory districts showing embedded condition of every layer and the sub-layer distribution are shown in Fig. 3-7.
(3) Behavior of groundwater
The groundwater level in the site is about 1 m beneath the surface. In some places the level is related to the rising and falling of the water level of the Shimi river, but it is domi-nated by seasonal rain fall. Generally, the ground water level for every year reaches its maximum in the flood season of September and reaches its minimum in the dry season of May. The shallow groundwater seeps from southwest to northeast with a slope of 1/50000.
2. Liquefaction of the Saturated Silt (II2)
(1) Delineation of the liquefied and unliquefied zone
On the basis of investigation of sand-water eruption and development of cracks and damage of buildings after the earthquake, the liquefied and unliquefied zones were delineated (Fig. 8). The liquefied zone is defined where the surface was cracked, sand-water eruption occurred, buildings were split and more severe tilting and subsidence took place. Similarly, the unliquefied zone is where no crack or eruption took place, buildings were only partly damaged and without major tilting or subsiding. By this delineation it is hard to avoid classifying sections into unliquefied zones if a sandy subsurface soil layer liquefied but no sand-water eruption took place.
(2) Embedded condition of the saturated silt (II2)
According to engineering geological investigation, liquefied and unliquefied zones are similar in aspects of their geomorphology, geological age, generic type and soil layer dis-tribution. The embedded condition of silt layer (II2) is shown in Table 1. We can see the smaller, average thickness of silt layers having slightly larger overburden pressure in the unliquefied zone.
(3) Experiment results of the silt layer (II2)
Statistical data of physical experiments for the silt layer (II2) are shown in Table 2. From the individual experiment specification we can see no apparent difference except the angle of internal friction between the silt of the liquefied zone and that of the unliquefied zone. The experiment for mechanical composition indicates that the average grain size of the silt in the unliquefied zone is smaller (i.e., silt and clay grain are in high content ) with larger coefficient of uniformity (Table 3). These two factors are favorable for the silt layer to resist liquefaction.
564
(4) In situ test of silt layer(II2)
(4.1) SPT results of silt layer(II2). Table 4 presents SPT blow count of the saturated silt layer(II2).
It can be seen that the average of SPT blow counts are different for the liquefied and unliquefied zones. The average blow count in the unliquefied zone is smaller than that of the liquefied zone. SPT blow count does not only depend on density and embedded depth, but also on the composition of soil grain size. The relation between SPT blow count and compo-sition proportion of grains of the silt for liquefied and unliquefied zones are shown in Fig. 9-11.
(4.2) Results of static cone penetration test of silt layer (II2)
From the results of the static cone penetration test for saturated silt (Table 5), and curves for specific penetration resistance (Ps) and depth (H) (Fig. 12.13), it can be seen that the average specific penetration resistance of the saturated silt in the unliquefied zone and that in the liquefied zone are 40 kg/cm2 and 50 kg/cm2 respectively. This tendency coincides with the results of SPT.
(Translators: Shi Zhaoji, Zhang Yuanyi)
Table 1. Embedded condition of silt layer (II2).
Embedded Maximum Minimum Average
condition Liq. zone Unliq. zone Liq. zone Unliq. zone Liq. zone Unliq. zone
Elevation of borehole (m)
4.5 4.54 3.69 4.10 4.23 4.35
Depth of upper
boundary (m) 2.60 3.10 2.00 2.50 2.38 2.95
Thickness (m)
3.80 2.50 3.00 1.00 3.55 1.85
Ground water level (m)
0.90 0.45 0.60 0.05 0.78 0.27
Overburden pressure
(t/m2) 4.75 6.01 4.18 5.49 4.47 5.6
565
Table 2. Statistical results of physical data of silt layer (II2).
Test Maximum Minimum Average
index Liq. zone Unliq. zone Liq. zone Unliq. zone Liq. zone Unliq. zone
Water content (%) 29.7 33.5 23.3 24.4 25.5 26.2
Wet unit weight (g/cm3) 2.02 2.01 1.86 1.75 1.95 1.92
Dry unit weight (g/cm3) 1.63 1.60 1.48 1.26 1.56 1.52
Specific gravity (g/cm3) 2.71 2.72 2.64 2.67 2.68 2.70
Degree of saturation (%) 100 100 80 87 94 92
Void ratio 0.82 1.17 0.63 0.68 0.72 0.78 Liquid limit
(%) 30.2 28.0 24.0 25.0 26.1 27.1 Plastic limit
(%) 22.9 19.8 14.9 16.4 18.8 18.2 Index of
plasticity (%) 9.8 10.0 4.5 7.4 7.3 8.9 Index of
liquidity (%) 1.38 1.61 0.42 0.67 0.92 0.95 Coefficient of
compressibility (cm2/kg)
0.033 0.039 0.006 0.010 0.014 0.019
Modulus of compressibility
(kg/cm2) 230 166 54 49 136.5 100
Angle of inter-nal friction
(degree) 37 35 31 20 34.4 29.1
Cohesion (kg/cm2) 0.23 0.30 0.06 0.10 0.15 0.20
Unconfined compression
strength (kg/cm2)
0.65 0.65 0.48 0.55 0.57 0.60
566
Table 3. Statistical data of graduation test of silt layer (II2).
Maximum Minimum Average
Item Liq. zone
Unliq. zone
Liq. zone
Unliq. zone
Liq. zone
Unliq. zone
Sand fraction (%) 2.0-0.5 0.5-0.25 0.25-0.10 0.10-0.05
— — 14 87
— — 2 77
— — 1 41
— — 1 47
— — 6 76
— — 1 60
Silt fraction (%) 0.05-0.01 0.01-0.005
44 5
40 7
4 1
12 3
11 3
26 4
Clay fraction (%) <0.005 12 12 1 5 4 9
Constrained diameter 0.094 0.063 0.052 0.052 0.076 0.056
Mean diameter 0.088 0.060 0.045 0.050 0.074 0.054
Effective diameter 0.054 0.011 0.004 0.004 0.031 0.006
Coefficient of uniformity (mm) 20.9 14.2 1.5 5.5 4.2 9.5
Table 4. N, SPT Blow count of saturated silt layer (II2).
N, SPT Liquefied zone Unliquefied zone
blow count 2-3(m) 3-4(m) 4-5(m) 5-6(m) 3-4(m) 4-5(m) 5-6(m)
Maximum 11.0 16.0 16.0 18.0 11.0 6.0 4.8
Minimum 6.6 5.6 4.7 5.0 4.7 3.0 2.9
average 8.8 9.0 10.9 9.1 6.8 4.7 3.9
567
Table 5. Specific penetration resistance of silt layer (II2).
Liquefied zone
No depth (m) thickness(m) Ps(kg /cm2) 1 2.5-5.3 2.8 66.6 2 2.6-6.0 3.4 44.5 3 3.0-5.8 2.8 47.0 4 2.9-5.3 2.4 53.0 5 3.0-5.8 2.8 68.0 6 2.8-6.0 3.2 51.5
average 55
unliquefied zone
No depth (m) thickness (m) Ps(kg /cm2) 1 3.1-4.1 1.0 38 2 3.0-4.0 1.0 47 3 3.2-4.3 1.1 41 4 3.0-4.1 1.1 44 5 3.0-4.3 1.3 44 6 2.6-3.8 1.2 37 7 2.9-4.0 1.1 40 8 3.0-4.0 1.0 42 9 2.8-4.0 1.2 37 10 3.0-4.2 1.2 28
average 40
Figure 1. Location map of the Tianjin Petroleum Chemical Plant.
568
Figure 2. Schematic map showing changes of the west coastal line of Bohai Bay.
Figure 3. Location map of borehole.
569
Figure 4. Profile of borehole No. 4 in General Petroleum Chemical Plant
(unit: mm) (by Geological Team Tianjin Construction Division,
16 May - 19 June, 1972).
Figure 5. Profile of borehole No. 62 in Petroleum Chemical Plant
(unit: mm) (by Survey Co., Dept. of Petroleum Industry,
10 June 1976).
570
Figure 6. Profile of borehole No. 55 in Polyester Division, Tianjin Chemical Fiber Plant (unit: m) (by No. 2 Design
Institute Dept. of Light Industry).
Figure 7. Profile of borehole No. 10 in residential area, No. 4 Chemical
Construction Co. (unit: mm) (by No. 3 Survey Team, Dept. of Petroleum
Industry, 22 October 1974).
Figure 8. Delineation of the liquefied and unliquefied zones.
571
Figure 9. Relationship between SPT blow count, N and sand content.
Figure 10. Relationship between SPT blow count, N and silt content.
Figure 11. Relationship between SPT blow count, N and clay content.
572
Figure 12. Ps−H curve of unliquefied zone.
Figure 13. Ps−H curve of liquefied zone.
573
CHARACTERISTICS OF LIQUEFIED SANDS IN BEIJING AND ITS ADJACENT AREAS DURING TANGSHAN EARTHQUAKE
Wang Kelu, Sheng Xuebin, Cai Lingduo, Hu Biru, Liu Huimin1
During the Tangshan earthquake of 1976, sand boils of ejected water and sand were widely distributed in the Beijing area. This section deals with the general characteristics of the ejected sands in Fangshan, Shunyi, Tongxian and Daxing counties of Beijing and Xianghe County of Hebei Province.
1. Distribution of the liquefied sands
During the 1976 earthquake, the seismic intensity in Beijing was from V to VIII and decreased east to west. The liquefaction of sandy soil had taken place mainly in the areas with intensity of VII and VIII. Ejected water and sands were found in a vast area from Yan-chuang village of Fangshan County in the west, to Menlou of Pinggu County in the east, and from Nihe village of Shunyi County in the north, to Caiyu village of Daxing County in the south. Severe liquefaction had been concentrated in the northeastern and southern parts of Beijing Plain, especially in Xiji Town and Langjiafu (or Langfu) village of Tongxian County, Wangjiachang village of Shunyi County and Caiyu village of Daxing County. The ejected water and sands were also occurred in Xianghe County, east of Beijing Plain (Fig. 1).
The distribution of liquefaction in the Beijing area was obviously zonal, the majority occurred in the frontal parts of alluvial and diluvial fans or in areas with high density in old river channels. The liquefied areas were often lower in topography, had a higher ground-water table (usually less than 3 meters under the ground surface), and contained development of subsurface silt and fine-grained sand layers. In these areas, the impermeable clay layer occurred in the upper part, silty and fine sandy layers in the middle and intermediate and coarse-grained sands, or gravel layers, in the lower part on the stratigraphic section. A typical geological profile is shown in Fig. 2.
Results of pollin analysis show that the plants in the middle layer of fine-grained sands and silt were mainly conifers, mixed with less broadleaf trees, Chenopodiaceae, Artemisia Gramineae and grass. The upper part contained mainly broadleaf trees and less conifers, while the lower part mainly was herb (Fig. 3 and 4).
From the available data it may be concluded that in the liquefied areas, the upper layer of soil was formed in the late Holocene, the middle layer in the middle Holocene, and the lower layer in early Holocene. For instance, the C14 dating of tree trunk taken from a depth of 15.5
1 All authors: Institute of Geology, State Seismological Bureau
574
m in the lower layer in Xiji Town gives an absolute age of 8250 ± 125 years2. This clearly indicates the lower layer must be early Holocene.
II. Composition of the liquefied sands
Analysis of granulometric, mineralogical and chemical compositions of the ejected sands were made after the earthquake. The obtained data are presented below.
1. Granulometric composition of the ejected sands
Analysis of the ejected sands from 12 locations in Xiji Town, Langfu Village and Xianghe County city indicates that the ejected materials are mainly sand-like soil (Table 1).
In order to make a comparison of the ejected sands with those in other areas, the granu-lometric composition of the ejected sands during Tangshan and Haicheng earthquakes are given in Table 2 and Fig. 5.
It can be seen from Table 2 and Fig. 5 that the ejected sands in Xiji and Langfu areas of Beijing, and Xianghe area, during the Tangshan earthquake were more coarse than those ejected in Pangjin and Yingkou of lower Liaohe River during the Haicheng earthquake. They were also more coarse than those ejected in the wide plain, including Tianjin and to the south of Lannan and Fengnan during the Tangshan earthquake. The fraction with grain size more than 0.05 mm was predominant, and fraction of 0.05-0.005 mm and of less than 0.005 mm were comparatively less in the Beijing area. The average size of the ejected sands is also larger than those ejected in Tianjin, Tangshan and the Lower Liaohe areas. Moreover, the un-uniformity coefficient of the sands is also less than that in Tianjin, Tangshan and the Lower Liaohe areas. For further comparison, the granulometric distribution of the ejected sands in different locations is given in Fig. 6.
2. Mineralogical composition of the ejected sands
Many kinds of minerals were found in the ejected sands and the undisturbed sand layer. Usually there were 25 or more kinds of minerals, with as many as 32 found. Quartz and feld-spar were the main light minerals, and augite and hornblende the dominant heavy minerals.
In order to further understand the characteristics of the ejected sands, various minerals of them were classified into four groups in accordance with their chemical stability, such as groups of unstable, nearly stable, stable and very stable minerals. The vastability coefficient of heavy minerals, k1 , is defined as the ratio of unstable minerals to stable plus very stable minerals. The ratio of feldspar to quartz is defined as the unstability coefficient of light minerals, k2. The greater k1 and k2 are, the easier the weathering of sand layers is. Analysis of the ejected and undisturbed sands in Xiji, Langfu and Xianghe areas (Table 3) indicated that the ejected sands contained more unstable minerals and had a greater unstability coeffi-
2The Geologic-Topographic Survey Branch of Beijing City, 1978, Report on the liquefaction of sandy soil in Xiji area of Tongxian County.
575
cient. Mineralogical composition of the sand layers at different depths in Lizhuang Village (unliquefied area) and Luozhiwang Village (liquefied area) is shown in Figs. 7 and 8 for comparative study. This characteristic was also reflected in ejected sands in the Tangshan and Tianjin areas.
We consider that a comparative study of mineralogical composition of the ejected sands with that of undisturbed original sands at different depths will provide information on depth of liquefaction. For purposes of comparison, the content of minerals are shown on the top of the columns in Fig. 8 and 9. Variation of the content and forms of minerals makes it possible to estimate the depth of liquefaction in Xiji Town to have been 12 m under the surface.
For particles less than 0.001 mm in diameter, differential thermal analysis, X-ray dif-fraction and electron microscope were used to determine the mineralogical composition. The results indicate that hydromica and montmorillonite were the main minerals of the ejected sands, iron oxides and quartz were less present (Table 4, and Fig. 10), but kaolinite was rare in individual samples.
3. Chemical composition of the ejected sands
Chemical composition of the ejected sands is shown in Table 5. It can be seen from Table 5 that NaHCO3 was the main soluble salt in the ejected sands, Na2SO4 was less, and NaCl and MgCl2 were rare components in the ejected sands.
Comparing the composition of ejected and undisturbed sands, we found that the content of organic materials, Cl− and Ca++, was higher in the ejected sands, but HCO3
- and Na+ + K+ were less in the ejected sands (Table 6).
Summarizing the results of granulometric, mineralogical and chemical analysis of the ejected sands, we can conclude:
(1) The ejected sands in Beijing and Xianghe areas are similar in granulometric compo-sition. The main characteristics of the sands are larger grain size, good sorting, and lower content of clay fraction. Therefore, they are different from those sands ejected in a wide onshore area south of Tangshan City, Tianjin and Lower Liaohe areas.
(2) The ejected sands contain many unstable minerals, and the unstability coefficient is very high. The fine-grained fraction contains a certain amount of montmorillonite. Augite, hornblende, feldspar and mica show evident weathering trace on their surfaces.
(3) PH value of the ejected sands is often more that 8, indicating that the ejected sands were formed in an alkaline environment. The ejected sands contain more organic materials, Cl-, Ca++ and less HCO3
- . This indicates that the ejected sands were formed under the con-ditions of a slower water flow.
(Translator: Wang Kelu)
576
Tabl
e 1.
Gra
nulo
met
ric c
ompo
sitio
n of
the
ejec
ted
sand
s in
Bei
jing
and
Xia
nghe
are
as.
Loca
tions
Se
ism
ic
Nam
e G
ranu
lom
etric
dis
tribu
tion
of sa
nds (
Φ=m
m)
Uns
ta-
bilit
y
Unu
n-ifo
rm-
ity
Text
ure
of sa
mpl
es
inte
n.
of so
il 0.
5-0.
25
mm
(%)
0.25
-0.1
m
m (%
) 0.
1-0.
05
mm
(%)
0.05
-0.
01
mm
(%)
0.01
-0.0
05
mm
(%)
0.00
5-0.
001
m
m (%
)
<0.0
01
mm
(%)
Ave
rage
co
effi-
cien
t co
effi-
cien
t co
effi-
cien
t
Xia
nghe
co
unty
Zh
angz
huan
g vi
llage
VII
Fi
ne
sand
79.1
9 14
.57
2.90
0.
50
0.56
2.
28
0.13
1.
27
2.13
2.
92
Huo
liuzh
ao
villa
ge
VII
V
ery
fine
sand
70.8
4 20
.76
5.10
0.
38
2.92
0.
00
0.13
1.
47
2.59
3.
01
Wes
t of
Jiaz
huan
g vi
llage
V
II
fine
sand
85.2
2 8.
98
3.42
0.
12
2.16
0.
00
0.12
1.
18
1.88
2.
21
Xia
nhe
city
V
II
fine
sand
71.5
2 23
.01
2.03
0.
99
2.45
0.
00
0.13
1.
60
2.13
2.
51
Quh
ou to
wn
VII
sa
ndy
loam
58.4
5 26
.24
8.62
1.
49
1.55
3.
65
0.11
1.
91
4.48
5.
49
Luoz
hiw
ang
villa
ge
VII
Fi
ne
sand
92.3
3 4.
68
0.78
1.
22
0.99
0.
00
0.15
1.
22
1.38
0.
10
Nor
th o
f X
ianc
unyi
ng
villa
ge
VII
Fi
ne
sand
75.6
5 16
.47
5.10
0.
34
2.44
0.
00
0.14
1.
48
2.40
2.
50
Ave
rage
76.1
7 16
.39
3.99
0.
72
1.87
0.
85
0.13
1.
45
3.43
2.
67
Bei
jing:
D
asha
wu
Ham
let o
f X
iji
VII
Sa
nd
loam
4.
68
52.9
5 28
.37
9.87
0.
42
3.71
0.
00
0.12
2.
67
4.06
3.
85
577
Tabl
e 1
(Con
tinue
d).
Gra
nulo
met
ric c
ompo
sitio
n of
the
ejec
ted
sand
s in
Bei
jing
and
Xia
nghe
are
as.
Loca
tions
Se
ism
ic
Nam
e G
ranu
lom
etric
dis
tribu
tion
of sa
nds (
Φ=m
m)
Uns
ta-
bilit
y
Unu
n-ifo
rm-
ity
Text
ure
of sa
mpl
es
inte
n.
of so
il 0.
5-0.
25
mm
(%)
0.25
-0.1
m
m (%
) 0.
1-0.
05
mm
(%)
0.05
-0.
01
mm
(%)
0.01
-0.0
05
mm
(%)
0.00
5-0.
001
m
m (%
)
<0.0
01
mm
(%)
Ave
rage
co
effi-
cien
t co
effi-
cien
t co
effi-
cien
t
Dah
uidi
an
Ham
let o
f X
iji T
own
VII
V
ery
fine
sand
3.
10
67.0
5 23
.37
3.31
0.
40
2.77
0.
00
0.13
2.
50
2.41
2.
85
Ave
rage
3.
89
60.0
0 25
.87
6.59
0.
41
3.24
0.
00
0.13
2.
59
3.24
3.
35
Bei
jing
:Lan
gxi
Ham
let o
f La
ngfu
vi
llage
VII
I Fi
ne
sand
38
.05
49.3
9 8.
19
2.32
0.
40
1.65
0.
00
0.21
1.
93
2.91
1.
68
Lang
fu
Ham
let o
f W
angz
huan
g vi
llage
VII
I Sa
nd
loam
1.
48
23.4
4 60
.25
10.8
8 0.
43
3.52
0.
05
0.08
1.
56
2.50
3.
65
Xiji
tow
n V
III
Sand
lo
am
3.05
39
.27
41.9
2 10
.13
1.28
4.
35
0.00
0.
09
2.12
2.
92
4.55
Ave
rage
14
.19
37.3
7 36
.79
7.78
0.
70
3.17
0.
00
0.13
1.
87
2.78
3.
29
Not
e: T
extu
re c
oeff
icie
nt =
Pe
rcen
tage
of g
rain
swith
dia
met
er <
0.00
5 m
mPe
rcen
tage
of g
rain
s with
dia
met
er >
0.0
05 m
m
Uns
tabi
lity
coef
ficie
nt =
Uns
tabl
e m
iner
als
Stab
le m
iner
als
578
Tabl
e 2.
Gra
nulo
met
ric c
ompo
sitio
n of
the
ejec
ted
sand
s in
diff
eren
t are
as d
urin
g H
aich
eng
and
Tang
shan
ear
thqu
akes
.
Loca
tion
Seis
mic
in
tens
ity
>0.0
5 m
m (%
) 0.
05-0
.005
m
m (%
) <0
.005
m
m (%
) N
onun
iform
ity
coef
ficie
nt
Ave
rage
gr
ain
size
(m
m)
Coe
ffic
ient
of
un
stab
ility
Text
ure
coef
ficie
nt
Num
ber o
f an
alyz
ed
sam
ple
Xiji
-Lan
gfu
area
, Bei
jing
VII
90
.21
7.00
3.
24
3.24
0.
13
2.59
3.
35
2
Xia
nghe
Cou
nty,
H
ebei
V
II
92.5
5 4.
71
2.19
2.
43
0.13
1.
45
2.67
7
Low
er X
ialia
ohe
area
V
II
67.7
5 24
.82
7.43
9.
10
0.06
—
—
14
Xiji
-Lan
gfu
area
, Bei
jing
VII
I 88
.35
4.48
3.
17
2.78
0.
13
1.87
3.
29
3
Tian
jin a
nd
Tang
shan
V
III
58.5
6 35
.14
6.29
5.
09
0.05
1.
98
6.79
7
Low
er X
ialia
ohe
area
V
III
82.5
0 12
.16
5.33
4.
09
0.09
—
—
6
579
Tabl
e 3.
Min
eral
ogic
al c
ompo
sitio
n of
the
ejec
ted
sand
s in
Bei
jing
and
its a
djac
ent a
reas
dur
ing
earth
quak
es.
Lith
olog
ical
ch
arac
teris
tics
Loca
tions
U
nsta
ble
min
eral
s (%
)
Nea
rly st
able
m
iner
als (
%)
Stab
le
min
eral
s (%
)
Ver
y st
able
m
iner
als
(%)
K1
Qua
rtz
(%)
Feld
spar
(%
) K
2
Gra
y fin
e sa
nd
Xiji
tow
n 69
.31
16.1
9 10
.17
3.95
4.
90
30.9
8 66
.40
2.14
Gra
y fin
e sa
nd
Wan
gzhu
ang
villa
ge
71.2
5 14
.98
12.7
5 0.
79
5.26
32
.56
64.1
8 1.
97
Gra
y fin
e sa
nd
Luoz
iwan
g vi
llage
73
.07
13.3
2 10
.61
2.96
5.
38
35.2
4 64
.76
1.84
Sand
loam
Q
ukou
vill
age
71.8
4 16
.23
9.06
2.
83
6.04
36
.36
63.6
4 1.
75
Fine
sand
X
iang
he c
ity
67.5
3 15
.75
14.2
3 2.
50
4.04
38
.02
61.9
7 1.
62
Fine
sand
X
iacu
nyin
g vi
llage
72
.25
12.8
8 12
.53
2.34
4.
86
35.6
6 64
.43
1.81
Fine
sand
H
angz
huan
g vi
llage
73
.96
13.3
4 11
.96
2.73
4.
89
36.0
7 63
.93
1.77
Fine
sand
W
est o
f Ji
azhu
ang
70.6
6 15
.59
12.1
5 2.
60
4.79
37
.09
62.9
0 1.
69
Ave
rage
70.9
8 14
.66
11.6
8 2.
59
5.02
35
.25
64.0
3 1.
82
580
Table 4. Clay minerals in the ejected sands in Beijing and Xianghe areas.
Kinds of soil
Locations Results of differential
thermal analysis
Results of electron microscope
analysis
Results of X-ray diffraction analysis
Fine sand
Xianghe county: city
Hydromica, mixed layer mineral of Hydromica--Montmorillonite, montmorillonite a little
Hydromica (mostly montmorillonized), less Montmorillonite and thin needle iron oxide
Hydromica, Hydromica-- Montmorillonite Kaolinite, Quartz, Iron Oxide
Fine sand
Luoziwang village
Hydromica, mixed layer mineral of Hydromica--montmorillonite,
Hydromica less montmorillonite Quartz, Amorphous colloid
—
Fine sand
Zhangzhuang village
Hydromica, less montmorillonite,
Hydromica (mostly montmorillonized),less Quartz
Hydromica, Chorite, Quartz
Fine sand
Xiacunying village
Hydromica, mixed layer mineral of Hydromica--montmorillonite, less montmorillonite
Hydromica (mostly montmorillonized), less Quartz
Chlorite, Hydromica, montmorillonite Iron Oxide
Sandy loam
Qukou village Hydromica, less montmorillonite,
Hydromica (mostly montmorillonized)
Hydromica, Hydromica-montmorillonite
Fine sand
Jiazhuang village
Hydromica, montmorillonite, less kaolinite —
Hydromica mixed layerof Hydromicamontmorillonite, Kaolinte,square Quartz
Sandy loam
Wangzhuang village of Tong Xian County — —
Mixed layer mineral of montmorillonite --Hydromica, Kaolinite
571
581
Tabl
e 5.
Che
mic
al c
ompo
sitio
n of
the
ejec
ted
sand
s in
Bei
jing
and
Xia
nghe
regi
on.
So
lubl
e
Con
tent
Io
ns e
xtra
cted
from
wat
er
Plac
e of
sa
mpl
ing
Seis
mic
in
tens
ity
Nam
e of
so
il sa
lts
(%)
PH
of
orga
nic
mat
eria
ls
(%)
HC
O3-
-
(m.e
%)
Cl-
(m
.e %
) SO
4--
(m.e
%)
Ca+
+
(m.e
%)
Mg+
+
(m.e
%)
KN
a+
++
(m.e
%)
Xia
nghe
co
unty
Zh
angz
huan
g vi
llage
V
II
Fine
sand
0.04
5 8.
63
0.06
0.
320
0.15
7 0.
134
0.16
8 0.
000
0.44
3
Huo
liuzh
ao
villa
ge
VII
V
ery
fine
sand
0.
042
8.78
0.
15
0.32
0 0.
102
0.13
4 0.
168
0.00
3 0.
354
Wes
t of
Jiaz
huan
g vi
llage
V
II
Fine
sand
0.06
8 8.
96
0.15
0.
483
0.20
4 0.
235
0.53
6 0.
034
0.35
2
Cou
nty
City
V
II
Fine
sand
0.05
7 8.
83
0.20
0.
511
0.11
0 0.
160
0.36
2 0.
000
0.41
9
Quk
ou v
illag
e V
II
Sand
y lo
am
0.09
5 8.
83
0.35
0.
540
0.28
2 0.
570
0.54
9 0.
556
0.28
7
Luoz
hiw
ang
villa
ge
VII
Fi
ne sa
nd0.
039
8.25
0.
13
0.24
9 0.
117
0.16
8 0.
134
0.06
7 0.
333
Nor
th o
f X
ianc
unyi
ng
villa
ge
VII
Fi
ne sa
nd0.
038
8.65
0.
11
0.28
4 0.
117
0.13
4 0.
201
0.06
7 0.
267
Ave
rage
0.
056
8.70
0.
16
0.38
7 0.
155
0.21
9 0.
303
0.10
4 0.
351
Bei
jing
Dah
uidi
an
villa
ge o
f Xiji
to
wn
VII
V
ery
fine
sand
0.
050
8.44
0.
12
0.34
7 0.
233
0.13
2 0.
365
0.09
9 0.
248
582
Tabl
e 5
(Con
tinue
d).
Che
mic
al c
ompo
sitio
n of
the
ejec
ted
sand
s in
Bei
jing
and
Xia
nghe
regi
on.
So
lubl
e
Con
tent
Io
ns e
xtra
cted
from
wat
er
Plac
e of
sa
mpl
ing
Seis
mic
in
tens
ity
Nam
e of
so
il sa
lts
(%)
PH
of
orga
nic
mat
eria
ls
(%)
HC
O3-
-
(m.e
%)
Cl-
(m
.e %
) SO
4--
(m.e
%)
Ca+
+
(m.e
%)
Mg+
+
(m.e
%)
KN
a+
++
(m.e
%)
Dai
shaw
u vi
llage
of X
iji
Tow
n V
II
Sand
y lo
am
0.04
4 8.
50
0.09
0.
224
0.23
3 0.
199
0.33
2 0.
199
0.12
5
Ave
rage
0.
047
8.47
0.
11
0.28
6 0.
233
0.16
6 0.
349
0.14
9 0.
187
Bei
jing
Lanx
i vi
llage
V
III
Fine
sand
0.05
4 —
0.
11
0.46
2 0.
155
0.13
3 0.
398
0.13
3 0.
219
Wan
gzhu
ang
villa
ge
VII
I Sa
nd
loam
0.
060
—
0.20
0.
358
0.23
3 0.
265
0.43
1 0.
099
0.32
6
Xiji
tow
n V
III
sand
lo
am
0.04
3 —
0.
18
0.25
5 0.
155
0.19
9 0.
265
0.13
3 0.
211
Ave
rage
0.
052
—
0.16
0.
358
0.18
1 0.
199
0.36
5 0.
122
0.25
2
571
583
Ta
ble
6. C
ompa
rison
of c
hem
ical
com
posi
tion
of e
ject
ed a
nd u
ndis
turb
ed o
rigin
al sa
nds.
Loca
tion
and
nam
e
Tota
l am
ount
of
solu
ble
salts
HC
O3-
-
(m.e
%)
Cl-
(m
.e %
)SO
4--
(m.e
%)
Ca+
+
(m.e
%)
Mg+
+
(m.e
%)
KN
a+
++
(m.e
%)
Org
anic
m
atte
r PH
Se
ism
ic
inte
nsit
y
Num
ber
of
sam
ples
Xia
nghe
co
unty
, Heb
ei
prov
. (ej
ecte
d sa
nds)
0.05
4 0.
386
0.15
4 0.
224
0.29
3 0.
024
0.36
0 0.
164
8.70
V
II
7
Tong
xian
co
unty
, Bei
jing
(eje
cted
sand
s)
0.04
7 0.
286
0.23
3 0.
166
0.34
8 0.
119
0.18
7 0.
105
8.47
V
II
2
Tong
xian
co
unty
, Bei
jing
(eje
cted
sand
s)
0.33
8 0.
346
0.18
1 0.
199
0.36
5 0.
122
0..2
52
0.16
0
VII
I 2
Xia
nghe
and
Li
zhua
ng a
reas
, H
ebei
pro
v.
(und
istu
rbed
or
igin
al sa
nds)
0.07
3 0.
539
0.12
4 0.
243
0.12
6 0.
107
0.77
1 0.
05
9.56
V
II
4
Not
e: 1
. All
data
in th
e ta
ble
are
aver
aged
.
2. X
iang
he a
nd L
izhu
ang
area
s hav
e no
t bee
n liq
uefie
d du
ring
earth
quak
es.
584
Figure 1. Sketch map showing distribution of ejected water and sands in Beijing and its adjacent areas.
Figure 2. Geological profile from Gonggeidian Hamlet to Yingjiahe village.
585
a. Number of wood pollens; b. Number of bush and herb pollens; c. Number of fern spores. Figure 3. Stratigraphic column showing results of pollin analysis of the
sands ejected in Dadongezhang village of Tongxian County.
Figure 4. Stratigraphic column showing results of pollin analysis of the ejected sands in Zhangzhuang village of Xianghe County.
586
Figure 5. Comparison of granulometric composition of the ejected sand in Beijing, Xianhe, and other areas during earthquakes.
587
Figure 6. Granulometric distribution of the ejected sands in different areas during Tangshan and Haicheng earthquakes.
588
Figure 7. Mineralogical composition of the sand layers at different depths in Lizhuang Village
Figure 8. Mineralogical composition of the sand layers at different depths in Luozhiwang Village
589
Figure 9. Mineralogical composition of the sand layers at different depths in Xiji Town.
590
Figure 10. Curves of differential thermal analysis of clays in ejected sands in Xianghe area.
591
INFORMATION ON SAND LIQUEFACTION IN XIJI DISTRICT, TONG COUNTY, BEIJING
Yao Binghua, Wang Hanqi*
1. General
During the Tangshan earthquake, sand boils occurred in an extensive area (about 60 km2) east of Xiji-Langfu, Tong County of Beijing; 120 km from Tangshan. But in Gonggeidian-Mafang, in the vicinity of Xiji-Langfu, no sand boils were found.
Around Genglou-Wangzhuang, Langfu commune, sand boils scattered densely, totaling more than 1000. Portions of the ground deformed or ground fissures occurred. The overlying layer in Genglou district was relatively thin which led to small sand boils with spouted sand. As reported by local inhabitants, the height of water blown out was 1-2 m. The overlying layer in the vicinity of Wangzhuang was comparatively thick, consisting of sparsely scattered large sand boils with large amounts of spouted sand. The largest amount was tens of cubic meters for one sand boil with diameter of 1-2 m. Height of water blown out in this case was up to 3-4 m. The spouted materials were fine and silty sand, of gray or brownish gray color. In some districts, although no sand boils occurred, the ground had changed into a wave shape. The underlying sand layer may have liquefied, but no sand was spouted to the surface. In the districts with a thicker overlying layer, sand blew out from fissures in the ground, e.g. in the Langfu Commune Middle School.
Earthquake damage induced by sand liquefaction is summarized as follows:
Single-story farm houses settled, tilted seriously or even collapsed. One extensively cul-tivated land was covered by spouted sand, with thickness up to 30 cm. About 2/3 of all pump wells were damaged seriously. For example, 11 of 15 wells in the Xiji Commune and Hezhang Brigade were blocked by spouted sand. Some hydraulic facilities, such as gates, culverts, etc., were also damaged to various extents.
In addition, the overlying layer in the district had been thinned due to excavation of cul-verts, therefore most sand boils occurred in the culvert bed, blocking the channel and caused the bank to crack and settle.
In order to study the conditions and discriminating criteria for sand liquefaction, site investigation and exploration has been performed by the Beijing Municipal Exploration Department twice in Xiji-Langfu district from August 1976 to July 1977. The area investigated was about 100 km2, as shown in Fig. 1.
* Both authors: Beijing Municipal Exploration Department
592
2. Investigation method and items
Macro-investigation on earthquake damage was carried out first, then distribution of damage to the ground surface, such as sand boils and ground fissures was verified. Based on the collected data and results of site exploration, effect of topography, morphology and geo-logical characteristics on liquefaction was revealed.
On the basis of the above investigation, two exploration profiles (I-I' in NS direction and II-II' in WE direction in Fig. 2) passing through the investigated area were arranged; in the liquefied area and the non-liquefied area respectively. Considering that the zone from Wangzhuang to Genglou was a zone where sand boils occurred seriously, this should be an area of significant investigation. Two shorter exploration profiles were also arranged in this zone (III-III' and IV-IV' in Fig. 2). Overall, there were 20 locations for exploration and measurement.
The main items for exploration and measurement were: verification of the formation type, period, distribution of strata and properties of the soil in the Quaternary deposited layers. This last area focused within a depth of 20 m under the surface; especially the thick-ness of the overlying layer, compactness of the sand layer, composition of sand particles and ground water level.
In order to ensure the quality of the standard penetration test, an impact boring method was used. A vacuum sand sampler instead of boring casing, and automatic free-release hammer was adopted. Sand samples for sieve analysis and other tests were taken for each boring.
Investigation results were compared with the exploration and measurement data taken in the liquefied and non-liquefied areas, and the comparison was used to analyze the effect of topography, morphology, geology and hydro-geology conditions on sand liquefaction.
3. The main investigation and exploration data
For the convenience of analysis, all collected data are divided into two categories, i.e. those collected from the liquefied area (category I) and those from the non-liquefied area (category II). Based on the seismic intensity, thickness of the overlying cohesive soil layer and compactness of the sand layer, data of category I are divided again into three sub-cate-gories, I1, I2 and I3; data of category II are divided again into two sub-categories, II1 , II2 .The related data for different exploration locations are listed in Table 1.
Based on the exploration data, four geological-lithology profiles are drawn (Fig. 3-6), with seismic intensity, effective overlying pressure and underground water level shown in the figures for each exploration location.
593
4. Effect of morphological and geological characteristics on sand liquefaction
(1) Effect of morphological characteristics on sand liquefaction
This district is located in the southeast of Beijing. In the range of the morphological unit in the alluvial plain, in the middle and down stream of Chaobaihe River, the surface relief is low and smooth. In the district, the Chaobaihe River Channel has changed several times. Fig. 7 shows the distribution of old river channels based on the modified aerial map.
The investigation showed that all liquefied areas were situated at the river bed, valley flat and depressed meanders in and downstream of recent rivers; especially in the intersection of old river channels of different periods such as the zone from Genglou to Wangzhuang. Rela-tively thick, loose silt and fine sand were newly deposited in the zone. Where the water table was high, and the overlying layer was comparatively thin, favorable conditions for sand liquefaction were formed. In the area south of the North canal, which had not been influ-enced by the recent migration of the old river, no sand boils were seen. Although portions of this area were in the liquefied zone, the relief was high, water table slightly deep and the overlying layer was relatively thick. In places not far from the center of Xiji Town, and where the relief was relatively depressed, some earth silos settled or tilted due to sand lique-faction.
(2) Effect of geological characteristics on sand liquefaction
1) The investigated area is located at the boundary zone between Daxing heave and Dachang sag tectonically. There is a NNE Xiadian-Mafang fault passing through the investi-gated area (Fig. 8). To the east of the fault, lie strata of the Paleozoic era buried more than 3000 m under the surface; while to the west, the depth of the Paleozoic strata is only 300-500 m. In the earthquake, damage to the east of the fault (Xiji-Langfu) was serious. Intensity was in the area of VII, VIII locally, and caused sand boils and ground fissures to occur exten-sively; damage to the west was slighter.
2). In the north of the investigated area, i.e., north of the south embankment of the north canal, the channel of the Chaobaihe River has been changed several times. The Quaternary deposit in this area is mainly thick stratum with fine alluvial particles. In this stratum, the main water-bearing layer is composed of silty fine sand and moderate sand, while the water-resisting layer is composed of cohesive soil. The underground water flows from NW to SE. Based on the information of the Hydro-geology Brigade, Beijing Geology Bureau, depth of the water table in this area was 2-4 m in the water-rich season of 1976. It is known that, just before the quake, the underground water level obviously increased with a variation of the level in the range of 1-3 m. According to the exploration and test data, the stratum within 20 m. under the surface can be divided into 4 layers.
The first layer is an overlying cohesive soil layer. Based on the spore powder analysis carried out by the Institute of Botany, Chinese Academy of Sciences, this layer is determined as post-Holocene epoch deposit. It is mainly composed of loam of brownish and gray color, slightly and moderately dense, soft plastic and plastic, moist and saturated. Light loam exists
594
in the layer locally, with thin lens of silt and fine sand, and the soil is rather soft and weak. Thickness of the layer is generally 4-6 m, with bottom elevation of 8.6-13.4 m.
The second layer is a silty sand layer, mainly responsible for liquefaction. Based on the above spore powder analysis, this layer is determined to be Holocene deposit of the middle and late period. In the middle of this layer, there exist moderate sand lens and thin intercala-tion of cohesive soil. The soil is of brownish or gray color, loose to moderately dense with uniform particles, and is saturated. Thickness of the layer is generally 4-6 m with bottom elevation of 3.6-7.5 m. The average standard penetration blow count is 12. Average particle size of the soil is 0.177 ±0.011 mm with an inhomogeneity coefficient of 2.52 ±0.14.
The third layer is a moderate sand layer with intercalations of fine sand and clayey soil. Based on C14 measurement of a block of wood taken from a depth of 15.5 m in a boring hole located at the Xiji commune, the geological time of the layer is estimated to be 8250 ±125 years. Based on the above spore powder analysis, this layer is a deposit from the early stages of the Holocene period. Soil of this layer is brownish or gray in color; moderately dense or dense. Thickness of the layer is generally 7-8 m, with bottom elevation of -2.7-3.5 m, and average standard penetration blow count of 46. Average particle size of the soil is 0.3000 ± 0.014 mm and the inhomogeneity coefficient is 3.28 ±0.16.
The fourth layer is an intercalation layer of cohesive and sandy soil, and is located in the south of the investigated area; i.e. from Matou Town to Matou broadcast station. This area is south of the south embankment, of the North canal, and exhibited no effects from migration of the river channel. The soil in this layer is apparently different from those in the area north of the south embankment. The overlying cohesive soil layer on the sand layer is very thick, generally about 8 m. The soil is of brownish color, plastic to hard plastic and stiff. Based on the comparison of strata, deposition time of this layer is relatively old. During this earth-quake, no sand boils were found in this area.
From the above-mentioned information on morphology, geology and the geological lithology profiles, it is found that thickness of overlying cohesive soil layers on saturated silt or fine sand has an obvious effect on liquefaction. In the north of the investigated area where the overlying layer is thinner (within 6 m) damage to ground surface, such as sand boils and ground fissures, occurred extensively. When thickness of the overlying layer is greater than 6-7 m, generally no sand boils were found, but sand would be blown out from the ground fis-sures, if they existed.
In the range north of the investigated area, the newly deposited loose silt and fine sand layers (average of standard penetration blows is 12) are those liable to liquefaction. Accord-ing to the spouted sand in the well of 10 m depth in Wangzhuang youth dormitory during the quake, it is shown that the liquefied depth was probably 10 m at least. In the investigation, no moderate sand was seen to be blown out.
(Translator: Lu Rongjian)
595
Tabl
e 1.
Soi
l lay
er d
ata
for d
iffer
ent e
xplo
ratio
n lo
catio
ns.
A
vera
ge v
alue
of s
tand
ard
pene
tratio
n bl
ows
Cat
egor
y of
dat
a N
o. o
f loc
atio
ns
Inte
nsity
D
epth
of u
nder
-gr
ound
wat
er
leve
l prio
r the
qu
ake
(m)
Thic
knes
s of
the
over
lyin
g co
hesi
ve so
il la
yer (
m)
Silty
fine
sand
laye
r (A
ve. p
artic
le si
ze:
0.17
7±0.
011
mm
)
Mod
erat
e sa
nd la
yer
(Ave
. par
ticle
size
0.3
0±0
.014
mm
St
atus
of l
ique
fact
ion
I 1
6
(Xiji
cer
eal
stor
age,
W
angz
huan
g yo
uth
dorm
itory
, W
angz
huan
g pl
aygr
ound
, W
angz
huan
g,
Feng
ezhu
ang,
Zh
angg
ezhu
ang)
VII
I ab
out 1
ab
out 3
.5-6
.4
12 (d
epth
, 3-7
m);1
6 (d
epth
, 7-1
2m)
25 (d
epth
abo
ve 1
2 m
).>50
(dep
th, u
nder
12
m)
sand
boi
ls o
ccur
red
gene
rally
, but
scat
-te
red,
rela
tivel
y la
rge
in a
mou
nt o
f san
d sp
out
I I 2
2
(Riv
er b
each
in
Mat
ou, a
co
urt i
n G
engl
ou
VII
I <1
.0
0 (s
ituat
ed in
th
e riv
er b
ed
and
valle
y fla
t of
the
exis
ting
Nor
th c
anal
)
9 (d
epth
, 1-
8 m
); 16
(dep
th, 8
-12
m)
26 (d
epth
, abo
ve 1
3.5
m)>
50 (d
epth
und
er
13.5
m)
sand
boi
ls o
ccur
red
gene
rally
, but
den
sely
; re
lativ
e sm
all i
n am
ount
of s
and
spou
ted
I 3
2 (L
angf
u m
id-
dle
scho
ol,
Hou
dong
yi)
VII
I no
t kno
wn
befo
re th
e qu
ake;
mea
s-ur
ed d
epth
in
expl
orat
ion,
2.6
-3.
4 m
(Jul
y,
1977
)
6.75
-6.9
20
in L
angf
u m
iddl
e sc
hool
(dep
th 7
-12
m);
20 in
Hou
dong
yi
(dep
th, 7
-8.5
m) a
nd
39 (d
epth
, 8.5
-10
m)
27 (d
epth
, abo
ve 1
3 m
; >3
0 (d
epth
, und
er 1
3 m
)
sand
with
wat
er b
low
n fr
om g
roun
d fis
sure
II
II1
5 (b
road
cast
st
atio
n of
M
atou
, a c
ourt
in M
atou
, Xiji
co
mm
une,
Y
injia
he,
Che
nhan
g)
VII
I (V
II in
Y
injia
he)
not k
now
n be
fore
the
quak
e; m
eas-
ured
dep
th in
ex
plor
atio
n, 1
-4
m (J
uly,
197
7)
6.6-
12.4
18
(dep
th, 6
-9m
); 26
(d
epth
, 9-1
1 m
) >4
0 (d
epth
und
er 1
1m)
no sa
nd b
oils
occ
urre
d
596
Tabl
e 1
(Con
tinue
d).
Soil
laye
r dat
a fo
r diff
eren
t exp
lora
tion
loca
tions
.
A
vera
ge v
alue
of s
tand
ard
pene
tratio
n bl
ows
Cat
egor
y of
dat
a N
o. o
f loc
atio
ns
Inte
nsity
D
epth
of u
nder
-gr
ound
wat
er
leve
l prio
r the
qu
ake
(m)
Thic
knes
s of
the
over
lyin
g co
hesi
ve so
il la
yer (
m)
Silty
fine
sand
laye
r (A
ve. p
artic
le si
ze:
0.17
7±0.
011
mm
)
Mod
erat
e sa
nd la
yer
(Ave
. par
ticle
size
0.3
0±0
.014
mm
St
atus
of l
ique
fact
ion
II
II2
2 (X
iege
zhua
ng,
Wan
gjun
tuan
) V
II
not k
now
n be
fore
the
quak
e 4.
5-5.
4 15
(dep
th, 4
.5-7
.0 m
); 26
(dep
th, 9
-11
m
belo
w)
24 (d
epth
, abo
ve 1
0 m
);>39
(dep
th, u
nder
10
m)
no sa
nd b
oils
occ
urre
d;
in th
e so
il co
lum
n ta
ken
from
the
over
ly-
ing
cohe
sive
soil
laye
r in
Wan
gjun
tuan
, a
long
itudi
nal s
tripe
of
sand
was
foun
d
3
(Xia
otun
, M
afan
g, M
afan
g m
iddl
e sc
hool
)
VII
in
Xia
otun
; V
I in
Maf
ang
not k
now
n be
fore
the
quak
e; m
eas-
ured
dep
th in
ex
plor
atio
n 1.
76-3
.30
m
(Jul
y, 1
977)
2.4-
4.4
5 (d
epth
, abo
ve 5
m
);10-
22 (d
epth
und
er
5 m
)
18 (d
epth
, abo
ve 1
2 m
);24
(dep
th, 1
2-18
m
);>50
(dep
th, u
nder
18
m)
no sa
nd b
oils
occ
urre
d
597
Figure 1. Sand liquefaction area in investigation.
Figure 2. Exploration profiles in the sand liquefaction area in Xiji-Langfu,
Tong County.
Figure 3. Geological lithology profile I-I' (in standard penetration test, weight of the hammer is 63.5 kg.; drop, 76 cm; penetration for each blow, 30 cm)
598
Figure 4. Geological lithology profile II-II' (in standard penetration test, weight of the hammer is 63.5 kg.; drop, 76 cm; penetration for each blow, 30 cm).
Figure 5. Geological lithology profile III-III' (in standard penetration test, weight of the hammer is 63.5 kg.; drop, 76 cm; penetration for each blow, 30 cm).
599
Figure 6. Geological lithology profile IV-IV' (in standard penetration test, weight of the hammer is 63.5 kg.; drop, 76 cm; penetration for each blow, 30 cm).
1. old river channel in the early period; 2. old river channel in the middle and late period.
Figure 7. Distribution of old river channels in the Xiji-Langfu district.
600
Figure 8. Schematic diagram showing tectonic system of the investigated area for sand liquefaction.