Environmental Engineering Reference
In-Depth Information
As can be observed, the CCL and GCL composite barriers illustrated in Figure
16.28 are practically equivalent, with the contaminant migration being governed
largely by diffusion. Therefore, the importance of the geomembrane is evident in
reducing the advective migration of contaminants when typical thickness and related
hydraulic conductivity of mineral barriers are taken into account. In this case the
geomembrane hides the higher permittivity of the GCL in comparison with the CCL,
which is the main reason why the overall performance of both types of composite
liners is almost fully equivalent under the given assumptions. On the other hand, the
pure diffusion coefficient of the geomembrane is generally some order of magnitude
lower than that of the mineral layers. The geomembrane is generally very thin, so its
contribution to the reduction of the diffusive flux is limited, particularly for some
organic compounds (see [SAN 01] for more details).
GEOMEMBRANE AND
COMPACTED CLAY LAYER
GEOMEMBRANE AND
GEOSYNTHETIC CLAY LAYER
Λ
= 7.76*10
-11
(m/s)
q = 2.50*10
-12
(m/s)
Q
0
= q
h0
*t
aq
= 3.17*10
-6
(m
2
/s)
Λ
= 7.89*10
-11
(m/s)
q = 3.25*10
-12
(m/s)
Q
0
= q
h0
*t
aq
= 3.17*10
-6
(m
2
/s)
R
c
= 0.0222 (-) @ x = l
R
c
= 0.0235 (-) @ x = l
J
h
/c
0
q
h0
= 0.0222
J
h
/c
0
q
h0
= 0.0235
Figure 16.28.
Comparison of steady-state transport performances of two composite liners
using GCL and CCL (see also Figure 16.22)
