Environmental Engineering Reference
In-Depth Information
100
Fine sand
First estimate of
S
r
= 15 %
10
5
10
15
20
0
Matric suction (
u
a
-
u
w
), kPa
(a)
Fine sand
1.0
(
u
a
-
u
w
)
b
Computed values of
S
e
using
S
r
= 15%
λ
λ
= pore-size distribution index,
defined as curve of negative
slope of effective degree of
saturation,
S
e
, versus matric suction,
u
a
- u
w
0.1
2nd estimate of
S
r
obtained by fitting
computed point on
straight line
0.01
s
-
-
s
r
s
r
s
e
=
1
1
4
10 15 20
Matric suction (
u
a
-
u
w
),
kPa
(b)
Figure 7.8
Determination of air-entry value
(u
a
−
u
w
)
b
, residual degree of saturation
S
r
,and
pore-size distribution index
λ
: (a) matric suction versus degree of saturation curve; (b) effective
degree of saturation versus matric suction curve (after Brooks and Corey, 1964).
Further details on how the coefficient-of-permeability
function can be estimated from the matric suction versus
degree of saturation curve (or the SWCC) are presented
in the following sections as well as under estimation
procedures for the permeability function.
saturated coefficient of permeability and the matric suction
versus degree of saturation relationship. The matric suction
versus degree of saturation curve exhibits hysteresis. Only
the drainage or drying curve is used to illustrate the con-
cepts and theory behind the estimation of the permeability
function. The soil structure is assumed to be incompressible.
There are three soil parameters that can be identified from
the matric suction versus degree of saturation curve: the
7.3.5 Relationship between Coefficient of Permeability
and Degree of Saturation
Burdine (1953) and Brooks and Corey (1964) suggested
that the permeability function could be obtained using the
air-entry value of the soil,
u
a
−
u
w
b
, the residual degree
of saturation,
S
r
, and the pore-size distribution index,
λ
.
Corey (1954) suggested visualizing these parameters on
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