Geology Reference
In-Depth Information
[C] Void Ratio
H
, can
be computed by subtracting the initial deformation dial reading at the
beginning of the very first loading from the deformation dial readings
corresponding to 100% primary consolidation for each respective load-
ing. The change in void ratio for each loading,
The change in thickness of the specimen for each loading,
Δ
e
, can then be calculated
by dividing each change in thickness of the specimen (
Δ
H
) by the height
Δ
H/H
s
. The void ratio for each
loading,
e
, can be determined by subtracting the change in void ratio (
of solid in the specimen (
H
s
); hence,
e
=
Δ
Δ
e
)
Δ
from the initial void ratio,
e
0
; hence,
e
=
e
0
-
e
.
Values of void ratio for each loading, along with respective applied
pressures, can be used to plot the required graph of void ratios versus
the logarithm of pressure (
e
- log
p
curve).
Δ
[D] Coefficient of Consolidation
For each load increment for which time-versus-deformation readings
were obtained, the coefficient of consolidation can be calculated using
the equation
0.196
H
2
t
50
(20-8)
c
v
where:
c
v
coefficient of consolidation, in.
2
/min
H
half the thickness of the test specimen at 50% consoli-
dation (because the specimen is drained on both top
and bottom in this test), in.
t
50
time to reach 50% consolidation, min
It should be emphasized that a determination of the coefficient of
consolidation must be made for each test loading. The values of coeffi-
cient of consolidation for each loading, together with corresponding
applied pressures, can be used to plot the required graph of coefficient
of consolidation versus the logarithm of pressure (
c
v
- log
p
curve).
A consolidation test was performed in the laboratory, and the following
data were obtained:
NUMERICAL
EXAMPLE
[A] Specimen Data
At beginning of test:
Diameter of specimen,
D
2.50 in.
Initial height of specimen,
H
0
0.780 in.
(i.e.,
1.981 cm
)
Mass of specimen ring plus specimen
208.48 g
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