Environmental Engineering Reference
In-Depth Information
w
p
PI = % Passing #200*PI
100
80
w
p
PI = 50
40
30
20
15
60
10
3
40
w
p
PI = 0.1
D
60
= 0.1 mm
D
60
= 1 mm
20
0
10
6
0.1
1
10
100
1000
10,000
100,000
Matric suction, kPa
Figure 5.121
Combined family of SWCCs for plastic and nonplastic soils (after Zapata, 1999).
w
p
PI = % Passing #200*PI
100
80
w
p
PI = 50
40
30
20
15
D
10
= 0.02 mm
60
D
10
= 0.03 mm
D
10
= 0.04 mm
D
10
= 0.06 mm
10
3
40
w
p
PI = 0.1
D
10
= 0.12 mm
20
0
10
6
0.1
1
10
100
1000
10,000
100,000
Matric suction, kPa
Figure 5.122
Combined family of SWCCs when using Torres model when
D
10
is the repre-
sentative particle size for nonplastic soils (after Torres, 2011).
It was also suggested that if the
D
10
particle diameter
was less than 0.020, the
a
f
fitting parameter should be set
to 1.28.
The slope of the SWCC
n
f
was found to be related to the
a
f
fitting parameter (i.e., the inflection point):
The above suggested fitting parameters for granular mate-
rials can be combined with the previously proposed equation
for plastic soils to produce the family of SWCCs shown in
Fig. 5.122.
0
.
0075
a
f
+
0
.
1133
a
f
−
0
.
3061
(5.106)
The
m
f
fitting parameter was also found to be related to
the
a
f
fitting parameter:
log
n
f
=−
0
.
3577
a
f
+
5.15 APPLICATION OF SWCC
It is not practical to undertake rigorous and costly tests
on unsaturated soils for routine geotechnical engineering
practice. As a result, a variety of practical, indirect method-
ologies and test procedures have emerged for quantifying
unsaturated soil property functions. These indirect proce-
dures have proven to be adequate for most routine geotech-
nical engineering problems (M.D. Fredlund, 2000a).
Indirect procedures for the estimation of unsaturated
soil property functions have primarily made use of the
0
.
0058
a
f
−
0
.
0933
a
f
+
0
.
3481
(5.107)
The soil suction at residual conditions,
ψ
r
, was found to
be relatively constant for all granular soils:
m
f
=
0
.
4069
a
f
+
ψ
r
=
100
.
0
(5.108)
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