Grading damaged geosynthetics, as follows:
Material
Damage
Small (19-cm2 or 3-in.2) pieces of geotextile were ripped
Double-sided geonet
off of the netting in two places.
Abraded in the center, about 32 cm2 ( 5 in.2). Blade did
TS 1000
not cause hole to form.
Geogrid
Was cut on the NE corner.
Test procedure
The tests consisted of three procedures--tank driving (trafficking), followed by
tank braking, and then tank pivoting. The condition of the geosynthetics were
assessed after each procedure was completed. For the trafficking, the tank was
driven over each test section 10 times. Five passes were at 11 to 16 km/hr (7 to 10
mph) and five passes were at 24 to 27 km/hr (15 to 17 mph).
In the brake tests, the tank was traveling at 24 km/hr (15 mph) when the brakes
were applied. They were applied just as the front of the tank reached the edge of
the geosynthetic.
After the brake test, pivot tests were conducted. In these tests, the tank was
driven onto the test section so that it was centered. Then the driver did a 180 turn
by holding one track stationary.
Results
Trafficking
Geosynthetics placed on the surface survived 10 tank passes with no apparent
damage. Materials with flexural stiffness (the double-sided geonet, the geogrid
and the geogrid-geotextile combination) bunched up into "high" bunches, stretch-
ing across the width of the material perpendicular to the direction of traffic. The
geogrid covered with TS 1000 bunched up the highest at 46 cm (18 in.) high. The
GTF 300 (woven slit film) slid around on the soil surface, and the TS 1000
deformed neatly into tracks made by the cleats in the tank treads. Since all bare
materials laid on the surface performed well for the trafficking and braking tests,
these tests were not conducted on the materials covered with gravel.
Braking
Except for a few geogrid strands being broken, no damage to any products
placed on the surface occurred.
Pivoting
Nothing survived the pivot tests on the uncovered materials; every product
sustained rips and tears across the width of the sample. Furthermore, the geogrid
and the TS 1000 became entangled in the tank sprockets and gears that drive the
tread, and required considerable time to remove.
For materials covered with gravel, Polyrock was the only product that sur-
vived the pivot tests. It pulled out of the soil (and was thus rendered useless until
repositioned), but it did not break or tear.
Product selection for further testing
Based on the results described above, the Polyrock and the double-sided
geonet were selected for further testing.
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