Environmental Engineering Reference
In-Depth Information
10
−
2
10
−
4
10
−
6
b
K
10
−
8
e
FIGURE 3.15
Effect of joint spacing and aperture on
hydraulic conductivity. (From Hock, E.
and Bray, J. W.,
Rock Slope Engineering,
Institute of Mining and Metallurgy,
London, 1977. With permission.)
10
−
10
0.01
0.05
0.1
0.5
1.0
Joint aperture e (mm)
a
Q
t
1
h
0
Overflow
h
t
A
h
h
1
L
A
L
q
Screen
Screen
(a)
(b)
FIGURE 3.16
Two types of laboratory permeameters: (a) constant-head test; (b) falling-head test.
Falling-Head Test
Flow observations are made on the rate of fall in the standpipe (Figure 3.16b). At time
t
,
the water level drops from
h
0
to
h
1
, and
k
(
a
L/
A
t
1
)(ln
h
0
/
h
1
)
(3.7)
3.3.4
In SituTesting
Seepage Tests in Soils
Tests include constant head, falling or variable head, and rising head. They are summa-
rized in terms of applicable field conditions, method, and procedure in
Table 3.15.
