Geosynthetics June/July 2022 - 40

GSI NEWS
GEOSYNTHETIC
INSTITUTE
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geosynthetic- institute.org
By George R. Koerner
New GSI test method for resistance
of conductive geosynthetics
T
he Geosynthetic Institute (GSI) has a new test method for resistance measured
across positions on conductive geosynthetics. Conductive geosynthetics contain an
electrically charged backing (usually a thin layer of polyolefin with letdowns containing
20%-30% carbon black) that allows leaks to be detected in lined systems without the need
for a conductive subgrade beneath the liner system.
This test method presents a technique for determining the resistivity of conductive
geosynthetics by way of a digital ohmmeter. It can be used for testing geomembranes or
geotextiles that incorporate a conductive layer. The layer is generally an outer skin that
is 3-10 mils (0.07-0.25 mm) thick. The test works best on smooth conductive materials.
The data obtained in this method is useful for quantifying how conductive the material is
from a manufacturing quality control (MQC) perspective.
Conductive-backed geosynthetics may be used in combination with electrical leak
George R. Koerner, Ph.D.,
P.E., CQA, is the director of
the Geosynthetic Institute
in Folsom, Pa.
location (ELL) surveys using the water puddle or water lance method-ASTM D7002
Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the
Water Puddle Method-or the arc testing survey-ASTM D7953 Standard Practice
for Electrical Leak Location on Exposed Geomembranes Using the Arc Testing
Method-to find the leak. Such materials should conform to the requirements of
ASTM D7852 Standard Practice for Use of an Electrically Conductive Geotextile for
Leak Location Surveys.
There are several limitations with completing ELL surveys on nonconductive-backed
geosynthetics that are duly overcome by conductive-backed geosynthetics of good quality.
Some of the limitations that are overcome for ELL surveys are as follows:
* A conductive subgrade is needed for current to flow from a source electrode through
a leak in the liner system.
* Subgrades may be frozen, dry or low-moisture, with little or no current flow through
which to complete the ELL survey.
* Flooding of the detection layer will not be required between the primary and secondary
liners of a double-lined facility if a conductive-backed geosynthetic is used.
* Wrinkles are an issue with field-deployed polyethylene geomembranes without normal
pressure from overburden. There is no need for intimate contact between the
geomembrane and subgrade when conductive geosynthetics are used. This means that
you can run an ELL survey anytime during the day.
All that is needed for this test is a multimeter, tape measure and protractor. One cuts 10
round specimens from across the roll width of the geosynthetic. The specimens are then
conditioned in a lab until they reach a temperature equilibrium of 69.8˚F ± 3.6˚F (21˚C
± 2˚C). The specimens are marked at 4-inch (100-mm) increments in the machine, bias
and transverse directions as shown in Figure 1a. The conductive skin is then touched by
one free lead near each mark around the perimeter of the circle while the other lead is
held fixed at the origin. If a resistance is recorded, the material is conductive, and if no
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Geosynthetics June/July 2022

Table of Contents for the Digital Edition of Geosynthetics June/July 2022

Geosynthetics June/July 2022 - Cover1
Geosynthetics June/July 2022 - Cover2
Geosynthetics June/July 2022 - 1
Geosynthetics June/July 2022 - 2
Geosynthetics June/July 2022 - 3
Geosynthetics June/July 2022 - 4
Geosynthetics June/July 2022 - 5
Geosynthetics June/July 2022 - 6
Geosynthetics June/July 2022 - 7
Geosynthetics June/July 2022 - 8
Geosynthetics June/July 2022 - 9
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Geosynthetics June/July 2022 - 12
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Geosynthetics June/July 2022 - 22
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Geosynthetics June/July 2022 - 27
Geosynthetics June/July 2022 - 28
Geosynthetics June/July 2022 - 29
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Geosynthetics June/July 2022 - 31
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Geosynthetics June/July 2022 - 34
Geosynthetics June/July 2022 - 35
Geosynthetics June/July 2022 - 36
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Geosynthetics June/July 2022 - 38
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Geosynthetics June/July 2022 - 40
Geosynthetics June/July 2022 - 41
Geosynthetics June/July 2022 - 42
Geosynthetics June/July 2022 - 43
Geosynthetics June/July 2022 - 44
Geosynthetics June/July 2022 - Cover3
Geosynthetics June/July 2022 - Cover4
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