Geotechnical News • December 2015
51
WASTE GEOTECHNICS
Materials and
methods
The testing
program investi-
gated the rainfall
runoff response
of two types
of soil cover
systems, namely
low hydraulic
conductivity
and capillary
barrier covers.
The low hydrau-
lic conductivity
covers were
represented by a
layer of Devon
silt 300mm thick.
The capillary
barrier covers
consisted of a
layer of Devon
silt 150mm
thick overlaying
another 150mm
thick layer of
Suncor Tailings
Beach sand.
A specially
designed funnel
was employed to
pluviate the soil into the flume. Place-
ment of soil was performed by initially
placing the spout of the funnel at the
bottom of the flume. The funnel was
filled with soil, and then slowly raised
along the flume’s axes of symmetry.
This placement procedure ensured that
the soil was deposited in a low-energy
state without any drop height. The
velocity of raising the funnel, which
controlled the density of the soil
profile, was maintained the same by
employing a mechanical movement
when lifting the funnel.
The testing criteria for each type of
cover system involved the applica-
tion of six rainfall intensities ranging
between 40-260 mm/hr for three days
duration (eight consecutive hours each
day). Testing considered two each
initial state of saturation.
sum-
marizes the different testing stages and
controlling parameters. During each
test, rainfall and runoff volume and
rate were measured simultaneously
in 15-minute increments. In addition,
the volumetric moisture content and
matric suction were recorded at two-
minute intervals. Plots of volumes and
rates of water balance components
versus time were thereof established.
Figure 1. A view of the overall laboratory setup depicting
a uniform layer of saturated silt.
Table 1 Stages and controlling parameters of the testing program.
Stages and duration of the tests
Cover type
Initial state I
40 mm/hr
II
55 mm/hr
III
90 mm/hr
IV
140 mm/hr
V
190 mm/hr
VI
260 mm/hr
Low hydraulic
conductivity
(silt profile)
saturated
unsaturated
55 hrs
55 hrs
33 hrs
103 hrs
33 hrs
103 hrs
130 hrs
33 hrs
80 hrs
33 hrs
33 hrs
33 hrs
Capillary
barrier profile
saturated
unsaturated
103 hrs
103 hrs
55 hrs
55 hrs
55 hrs
55 hrs
33 hrs
55 hrs
45 hrs
55 hrs
33 hrs
55 hrs
