Geology Reference
In-Depth Information
Data collected during this test consist of the following:
DATA
Mass of permeameter (mold) with base plate and gasket attached (g)
Mass of permeameter (mold) with base plate and gasket attached
plus soil (g)
Length of specimen,
L
(cm)
Diameter of specimen,
D
(cm)
For water content determination:
Mass of air-dried soil plus can (g)
Mass of oven-dried soil plus can (g)
Mass of can (g)
Cross-sectional area of standpipe (burette),
a
(cm
2
)
Hydraulic head at beginning of test [see “Procedure,” step (7),
and Figure 19-1],
h
1
(cm)
Hydraulic head at end of test [see “Procedure,” step (8), and
Figure 19-1],
h
2
(cm)
Total time for water in burette to drop from
h
1
to
h
2
,
t
(s)
Temperature of water,
T
(°C)
CALCULATIONS
[A] Unit Weight Determination
Values of the unit weight of the air-dried soil specimen, water content of
the air-dried soil, dry unit weight of the soil specimen, and void ratio can
be computed in the same manner as related in Chapter 18.
[B] Permeability Test
The coefficient of permeability can be computed using equation [1]
h
1
h
2
2.3
aL
At
(19-1)
k
log
where:
k
coefficient of permeability, cm/s
a
cross-sectional area of standpipe (burette), cm
2
L
length of specimen, cm
A
cross-sectional area of soil specimen, cm
2
h
1
hydraulic head at beginning of test, cm
h
2
hydraulic head at end of test, cm
total time for water in burette to drop from
h
1
to
h
2
,s
The permeability computed using Eq. (19-1) is the value for the
particular water temperature at which the test was conducted. It is nec-
essary to correct this permeability to that for 20°C by multiplying the
computed value by the ratio of viscosity of water at the test temperature
to viscosity of water at 20°C (see Table 18-2, page 260).
t
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