Geosynthetics April/May 2023 - 8
Q &
UNDERSTANDING
GEOMEMBRANE ASPERITY
THE GEOSYNTHETIC
INSTITUTE ANSWERS
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Q: Twice in the past few weeks colleagues
asked me the same question about
geomembrane asperity, so I come to you
to understand it.
* Manufacturers tell us not to have a
requirement regarding the " minimum of
10 readings must average specified height.
Eight of the readings must be >= ... " , or
* Delete the acceptance criteria for asperity
that says: " The minimum average of each
sheet must be greater than the minimum
average as established by the interface
shear results. "
One manufacturer mentioned this criterion
caused problems in a project in Ohio. Did
GRI-GM13 have a requirement related to this
in the past? If so, why has that changed?
A: I think there is some confusion between
core thickness (ASTM D5994) Standard
Test Method for Measuring Core Thickness
of Textured Geomembranes and asperity
height (ASTM D7466) Standard Test Method
for Measuring the Asperity Height of
Textured Geomembrane. Asperity height
A
GMA TECHLINE
MODERATED BY
George R. Koerner
has always been 16 mils (0.4 mm) minimum
average in GRI-GM13. On February 20, 2006,
Revision 7 added a footnote on asperity
height clarification with respect to shear
strength to the tables. On November 4,
2015, Revision 13 removed the footnote
due to a protest by the manufacturers
that GRI-GM13 is a Manufacturing Quality
Control (MQC) specification and we should
not reference a performance test in it. In
short, clients were asking them to run direct
shear tests on their geomembrane prior to
shipment. This was felt to be way beyond
the intent of the specification.
In contrast, core thickness does have three
criteria in the specification (minimum
average thickness, lowest individual
for eight out of 10 values, and lowest
individual for any of the 10 values). This was
a compromise, knowing the variability of
many textured geomembranes.
What really matters is the performance of
the measured shear strength of the interface
in question. All of this asperity conversation
has a rough correlation with shear strength.
This work needs to be done with sitespecific
parameters in mind by a third-party
laboratory directed by the engineer of record.
8
Geosynthetics | April May 2023
http://www.geosyntheticsmagazine.com/
Geosynthetics April/May 2023
Table of Contents for the Digital Edition of Geosynthetics April/May 2023
Geosynthetics April/May 2023 - Cover1
Geosynthetics April/May 2023 - Cover2
Geosynthetics April/May 2023 - 1
Geosynthetics April/May 2023 - 2
Geosynthetics April/May 2023 - 3
Geosynthetics April/May 2023 - 4
Geosynthetics April/May 2023 - 5
Geosynthetics April/May 2023 - 6
Geosynthetics April/May 2023 - 7
Geosynthetics April/May 2023 - 8
Geosynthetics April/May 2023 - 9
Geosynthetics April/May 2023 - 10
Geosynthetics April/May 2023 - 11
Geosynthetics April/May 2023 - 12
Geosynthetics April/May 2023 - 13
Geosynthetics April/May 2023 - 14
Geosynthetics April/May 2023 - 15
Geosynthetics April/May 2023 - 16
Geosynthetics April/May 2023 - 17
Geosynthetics April/May 2023 - 18
Geosynthetics April/May 2023 - 19
Geosynthetics April/May 2023 - 20
Geosynthetics April/May 2023 - 21
Geosynthetics April/May 2023 - 22
Geosynthetics April/May 2023 - 23
Geosynthetics April/May 2023 - 24
Geosynthetics April/May 2023 - 25
Geosynthetics April/May 2023 - 26
Geosynthetics April/May 2023 - 27
Geosynthetics April/May 2023 - 28
Geosynthetics April/May 2023 - 29
Geosynthetics April/May 2023 - 30
Geosynthetics April/May 2023 - 31
Geosynthetics April/May 2023 - 32
Geosynthetics April/May 2023 - 33
Geosynthetics April/May 2023 - 34
Geosynthetics April/May 2023 - 35
Geosynthetics April/May 2023 - 36
Geosynthetics April/May 2023 - 37
Geosynthetics April/May 2023 - 38
Geosynthetics April/May 2023 - 39
Geosynthetics April/May 2023 - 40
Geosynthetics April/May 2023 - 41
Geosynthetics April/May 2023 - 42
Geosynthetics April/May 2023 - 43
Geosynthetics April/May 2023 - 44
Geosynthetics April/May 2023 - Cover3
Geosynthetics April/May 2023 - Cover4
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