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100
RS1
RS2
80
RS3
60
40
20
0
0.001
0.01
0.1
1
10
100
Grain size (mm)
Fig. 8.13. Three kinds of particlegradation forriver soilsmixed withnonplastic fines
Relativedensity, D r ,isapertinentparametertoevaluatemechanicalpropertiesofgranu-
lar soils of different particle gradations and defined by soil dry density
ρ
based on maxi-
mum and minimum dry densities,
ρ max and
ρ min , respectively, as
1
min
1
Dr
=
max ×
100%
(8.7)
1
min
1
Here,
ρ min weredeterminedbyastandardizedtestmethodofJapaneseGeotech-
nical Society utilizing a soil mold of 195mm inner diameter and 200mm depth. For the
maximum density
ρ max and
ρ max , soil was compacted in the mold by a vibrating disc in five lay-
ers. For the minimum density
ρ min , soil was gently placed into the mold through a metal
funnel elevated slowly with zero drop height. Details of the test method are described in
Hara and Kokusho (2004). Figure 8.14 shows relationships of maximum and minimum
densities versus fines content obtained for the soil materials used in this research. If the
data at Fc
0% is concerned, both minimum and maximum densities tend to increase
fromRS1 to RS3 withincreasing Cu .
=
3.2. TEST METHOD
In a triaxial apparatus used in this research, the specimen size was 100mm in diameter
and 200mm in height. The diameter of 100mm was about five times the maximum
particle size of RS3. The soil specimen was loaded cyclically by a pneumatic actuator
from above as a stress-control test as indicated in Figure 8.15. The soil specimens were
prepared by wet tamping because other preparation methods such as air-pluviation or
water-pluviation tend to intensify soil particle segregation for well-graded granular soils
containing fines. The relative density of the specimen was approximately adjusted to
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