Geosynthetics August/September 2020 - 24

CCR landfill final cover test pad-Part 1

the placement and compaction equipment length of 12 feet (3.7 m). The test
pad was constructed in September and
October of 2016.

Construction of subgrade,
geosynthetics and cover soil

Processed and
unprocessed soil

FIGURE 5 Root rake used to remove
particles larger than 4 inches (10 cm)
from processed soil

To obtain final cover soil with a maximum particle size of 9 inches (22.9 cm),
roots and rocks larger than 9 inches
(22.9 cm) were removed. This sub 9-inch
(22.9-cm) particle soil was referred to as
"unprocessed soil."
To prepare "processed" soil, a root
rake was used to remove rocks, roots
and woody material greater than 4 inches
(10.2 cm) (Figure 5). Both processed and
unprocessed soils classified as gravelly
lean clay with sand (USCS CL).

Test pad subareas

The test pad layout is shown in Figure 6.
The test pad was divided into subareas to
allow testing of various combinations of
conditions, such as the subgrade protrusion height, cover soil lift thickness, cover
soil maximum rock size and subareas with
cushion geotextile. The resulting combinations of materials tested in the various test
pad subareas are presented in Table 1. Test

Test Pad
Portion

Maximum Angular
Subgrade Protrusion
inches (cm)

A

Cover Soil Lift Thickness

conditions for adjacent Subareas C and
E were identical, and test conditions for
adjacent Subareas D and F were identical.

Subgrade preparation and
subgrade protrusion placement
The subgrade was proof-rolled prior to
installation of the geomembrane. Since
proof-rolling resulted in a smooth subgrade, and one purpose of the test pad
was to evaluate the effect of subgrade protrusions, American Association of State
Highway and Transportation Officials
(AASHTO) No. 57 angular, crushed
aggregate was scattered over a small area
within each subarea of the prepared subgrade. One larger rock was also placed in
each subarea near the No. 57 aggregate
to create approximately 1-inch (2.5-cm)
protrusions. The center of each area of
placed aggregate was surveyed so that
it could be located during subsequent
exhuming of the test pad.
IDS geomembrane and IDS
geotextile installation and testing
The IDS geomembrane was installed over
the prepared subgrade with the embossed
spikes facing down against the subgrade

Cover Soil Maximum
Rock Size, First Lift
inches (cm)

Cushion Geotextile
Between Subgrade and
Geomembrane?

First Lift inches
(cm)

Second Lift
inches (cm)

1 (2.5)

12 (30.5)

6 (15)

4 (10)

No

B

1 (2.5)

18 (46)

NA

9 (23)

No

C&E

1 (2.5)

12 (30.5)

6 (15)

4 (10)

Yes

D&F

1 (2.5)

18 (46)

NA

9 (23)

No

NA = Not applicable
TABLE 1 Combinations of materials tested
24

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Geosynthetics August/September 2020

Table of Contents for the Digital Edition of Geosynthetics August/September 2020

Geosynthetics August/September 2020 - Cover1
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Geosynthetics August/September 2020 - 1
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