Environmental Engineering Reference
In-Depth Information
Equation 14.33 reduces to the following form:
log
2
i
log
r
C
s
rH
j
−
1
h
ri
=
+
(14.34)
1
+
e
0
2
j
Equation 14.34 can be applied to all layers in the wetted
zone to give the total heave:
r
1
j
log
r
log
2
i
j
C
s
H
1
−
1
H
r
=
+
(14.35)
+
e
0
2
j
i
=
1
Substituting Eq. 14.27 into Eq. 14.35 for
j
=
35 gives
C
s
H
1
H
r
=
r(
−
0
.
430
+
log
r)
(14.36)
+
e
0
1.0, the entire active depth is wetted, and
Eq. 14.36 reverts to Eq. 14.27. A comparison between
Eq. 14.36 and Eq. 14.27 can be written as follows:
When
r
=
H
r
H
=
r(
1
−
2
.
326 log
r)
(14.37)
Figure 14.48
Effect of correcting swelling pressure on computed
change in void ratio for various overburden pressures.
Figure 14.50 shows a plot of the above equation
where various percentages of the profile are wetted. The
relationship is unique for all values of swelling pressure
and swelling index. For example, it can be seen that 80%
of the total heave occurs if the depth of wetting is 40-50%
of the active depth. This example illustrates that it may
be possible to flood an area prior to construction until a
significant percentage of total heave has occurred. Whether
this is a practical engineering solution may depend on other
factors such as the hydraulic soil properties and the design
of the structure.
Figure 14.49
Stress distributions and definition of variables for
wetting portion of soil in active depth.
The heave for any layer in the wetted zone can be calcu-
lated by substituting the variables shown in Fig. 14.49 into
Eq. 14.18:
log
ρ
grH
(
2
i
C
s
rH
j
−
1
)/
2
j
h
ri
=
(14.33)
+
e
0
ρ
gH
1
where:
h
ri
=
heave of an individual layer when a portion of
the active depth is wetted and
Figure 14.50
Ratio of total heave predicted for wetting over por-
tion of depth as ratio of total heave when wetting entire active
depth.
r
=
portion of the profile wetted (i.e.,
H
r
/H
).
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