Geosynthetics June/July 2020 - 17

GCL and the foundation soil observed
during the exhumation process. While
it is expected that moisture equilibrium
between the GCL and the underlying
soil (i.e., relatively constant water contents for both materials at all locations) would have been reached over
the 12-year period that the liner system
remained in place at the site, moisture
content of the GCL was variable at the
site. This variation in moisture content
likely resulted from the movement of
water as a result of condensation that
formed between the geomembrane
and the GCL due to diurnal temperature variations and also from moisture
accumulation near the sump location
at the landfill cell. Bentonite likely was
carried down with condensate water.
The migration of bentonite reduced the
amount of bentonite in the GCL in the
upper parts of the slopes. This bentonite
was accumulated on the GCL at lower
elevations (in the wedge as a distinct
mass and on the GCL panels deposited
as stripes). The presence of subgrade
soil between the geomembrane and the
GCL (at the mountain) prevented intimate contact of the geomembrane and
GCL, forming a potential pathway for
fluid transfer. The bentonite loss toward
the toe of the slope was near the sump;
it is expected that significant wetting/
drying and accompanying changes in
level of standing water occurred at this
location due to annual precipitation
cycles. Bentonite between the geotextile
sheets of the GCL may have been eroded
due to hydrodynamic forces associated
with precipitation water entering the
uncovered cell at the site. Low bentonite content in GCLs near toes of slopes
has not previously been reported in the
literature. The seasonal ponding at the
south end of the cell also may have influenced the accumulation of subgrade soil
between the geomembrane and GCL
(the mountain feature).

FIGURE 7 GCL sample with significant loss of bentonite

1

2

2.630
0.160

0.100

0.030

FIGURE 8 Schematic section of mountain (dimensions in meters)

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Geosynthetics June/July 2020

Table of Contents for the Digital Edition of Geosynthetics June/July 2020

Geosynthetics June/July 2020 - Cover1
Geosynthetics June/July 2020 - Cover2
Geosynthetics June/July 2020 - 1
Geosynthetics June/July 2020 - 2
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Geosynthetics June/July 2020 - Cover3
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