1131
Technical Committee 106 /
Comité technique 106
The pore-air pressure of 98kPa indicates atmospheric pressure.
Air permeability increases with decrease in the degree of
saturation. Therefore, air can be drained easily on the specimen
with lower moisture, while air pressure increases due to air
entrapment on the specimen with higher moisture. Air pressure
remains the same even after compaction due to drainage
difficulty in the specimen with higher moisture. When air
pressure change is fairly small, the suction change corresponds
to the change in water pressure.
Figure 12 shows compaction curves, namely the relationship
between water content and dry density obtained from static
compaction simulations. This shows the maximum dry density
at the optimum water content and the shapes agree with the
actual compaction curve. The increase in maximum dry density
and the decrease in the optimum water content with increase in
the compaction load are expressed well here. Distributions for
state quantities on the specimen compacted under 400kPa
compaction load are introduced here. Figure 13 shows
distributions for the degree of saturation after compaction. The
specimen with higher moisture shows higher degree of
saturation totally. Uniform distribution appears on the specimen
with lower moisture. On the other hand, degree of saturation
tends to increase gradually when it approaches the air-drained
boundary. In the region over the optimum water content (about
24%), high degree of saturation appears only around the air-
drained boundary since air permeability is fairly low. Figure 14
shows distributions of void ratio. There are different tendencies
depending on whether it is under or above the optimum water
0.7
0.75
0.8
0.85
Time
t
(min)
Void ratio
e
(-)
Unloading (1min)
Loading (1min)
：
w
=14%
：
w
=18%
：
w
=22%
：
w
=26%
0.4
0.5
0.6
0.7
0.8
0.9
1
Time
t
(min)
Degree of saturation
S
r
(-)
Unloading (1min)
Loading (1min)
w
=26%
w
=22%
w
=18%
w
=14%
0
50 100 150 200 250
0.4
0.6
0.8
1
Degree of saturation
S
r
(-)
Suction
s
(kPa)
w
=14%
w
=18%
w
=22%
w
=26%
Loading
Unloading
Figure 6. Changes in void ratio of element
○
,
3
Figure 7. Changes in degree of saturation
Figure 8. Soil water retention characteristics
of element
○
,
3
during compaction
0
50
100
150
200
250
Time
t
(min)
Suction
s
(kPa)
Unloading (1min)
Loading (1min)
w
=14%
w
=18%
w
=22%
w
=26% 100
200
300
Time
t
(min)
Air pressure
p
a
(kPa)
Unloading (1min)
Loading (1min)
w
=14%
w
=18%
w
=22%
w
=26%
-100
0
100
200
Time
t
(min)
Water pressure
p
w
(kPa)
Unloading (1min)
Loading (1min)
w
=14%
w
=18%
w
=22%
w
=26%
Figure 9. Changes in suction of element
○
,
3
Figure 10. Changes in pore-air pressure
Figure 11. Changes in pore-water pressure
of element
○
,
3
of element
○
,
3
10
20
30
1.5
1.6
1.7
Water content
w
(%)
Dry density
d
(g/cm
3
)
S
r
=1.0
S
r
=0.9
S
r
=0.8
400(kPa)
800(kPa)
1600(kPa)
0.7
0.8
0.9
1
0
0.5
1
1.5
2
Degree of saturation
S
r
(-)
Height
h
(cm)
w
=20%
w
=22%
w
=24%
w
=26%
w
=28%
0.7
0.75
0.8
0
0.5
1
1.5
2
Void ratio
e
(-)
Height
h
(m)
w
=20%
w
=22%
w
=24%
w
=26%
w
=28%
Figure 12. Water content - dry density relation
Figure 13. Distributions of saturation
Figure 14. Distributions of void ratio
0.7
0.71 0.72 0.73 0.74
0
0.5
1
1.5
2
Void ratio
e
(-)
Height
h
(cm)
400(kPa)
w
=22%
400(kPa)
w
=26%
800(kPa)
w
=18%
800(kPa)
w
=26%
1600(kPa)
w
=14%
1600(kPa)
w
=26%
10
20
30
100
500
1000
Water content
w
(%)
400(kPa)
800(kPa)
1600(kPa)
Yield stress
p'
c
(kPa)
Figure 15. Distribution of void ratio on same dry density
Figure 16. Water content – consolidation yield stress relation
