Civil Engineering Reference
In-Depth Information
or
al
Ak
dh
h
dt
=−
Integrating between the test limits:
t
=−
al
Ak
h
1
2
∫
∫
dt
h
dh
0
h
1
i.e.
al
Ak
h
h
al
Ak
h
h
2
1
t
=−
ln
=
ln
1
2
or
al
At
h
h
al
At
1
2
k
=
ln
h
h
1
=
2 3
.
log
10
2
Example 2.2:
Falling head permeameter
An undisturbed soil sample was tested in a falling head permeameter. The results were:
Initial head of water in stand pipe
=
1500 mm
Final head of water in stand pipe
=
605 mm
Duration of test
=
281 s
Sample length
=
150 mm
Sample diameter
=
100 mm
Stand-pipe diameter
=
5 mm
Determine the permeability of the soil in m/s.
Solution:
π
×
5
4
2
π
×
100
4
2
2
2
a
=
=
19 67
.
mm A
=
=
7854
mm
h
h
=
1
2
log
log
10
2 48
.
=
0 3945
.
10
2 3 19 67 150 0 3945
7854 281
.
×
.
×
×
.
−
3
−
6
k
=
=
1 21 10
.
×
mm s
/
=
1 2 10
.
×
m s
/
×
2.5.3 The hydraulic consolidation cell (Rowe cell)
The Rowe cell (described in Chapter
11
) was developed for carrying out consolidation tests. The apparatus
can also be used for determining the permeability of a soil. The test procedure is described in BS 1377:
Part 6.
