Environmental Engineering Reference
In-Depth Information
1.05
1.00
P
1-1
= 550-710 kPa
P
1-2
= 710-790 kPa
0.95
0.90
0.85
0.80
e
0
(Initial void ratio)
0.75
1
10
Total stress, kPa
100
1000
Figure 14.29
Swelling pressures measured when using loading-after-swell procedure from sur-
charge pressures of 5, 50, 100, 200, and 400 kPa (from Feng et al., 1998).
1.05
Specimen 1
1.00
After full swell
0.95
P
2-1
= 490 kPa
P
2-2
= 1050 kPa
2
0.90
3
4
0.85
5
e
0
(Initial void ratio)
0.80
6
7
8
0.75
Before inundation
0.70
0.65
1
10
100
1000
10,000
Surcharge pressure (kPa)
Figure 14.30
Swelling pressures measured when using swell-under-load procedure on eight
specimens subjected to various surcharge pressures (after Feng et al., 1998).
full-swell curve and the before-inundation curve to define
swelling pressure (i.e.,
P
2
−
2
). The first definition (i.e.,
P
2
−
1
)
gave a swell pressure value of 490 kPa and the second defini-
tion (i.e.,
P
2
−
2
) gave a swelling pressure value of 1050 kPa.
The swelling pressure
P
2
−
2
would appear to be more mean-
ingful since it corresponds to the surcharge pressure under
which the soil was brought to equilibrium. The soil could not
undergo any further volume change under further wetting.
applied to the soil specimen (ASTM, 1986). The soil spec-
imen was then inundated. The vertical pressure on the soil
specimen was increased to prevent swelling as the specimen
imbibed water. The specimen was then loaded in accordance
with a conventional consolidation test procedure.
The vertical pressure corresponding to the end of wetting
under constant-volume conditions was defined as swelling
pressure
P
3
−
1
(Justo et al., 1984; Sridharan et al., 1986);
Chen, 1988; ASTM, 1986). The swelling pressure could
also be corrected for the effect of sampling disturbance. The
correction procedure gives rise to a corrected swelling pres-
sure
P
3
−
2
. The construction procedure proposed by Fredlund
14.4.11.3 Constant-Volume Test Procedure
The constant-volume tests performed by Feng et al., (1998)
were described as follows. A surcharge pressure was first
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