Geosynthetics June/July 2022 - 10

Q & A: GMA Techline
GEOTEXTILE GRAB TEST METHODS
FIGURE 1 Proper grab tensile grip faces.
Photograph courtesy of GSI
Q: I know the American Society for Testing
and Materials (ASTM) approves several grips
(the requirement is they be " flat " ) to perform
ASTM D4632 and ASTM D5034. We use a
hard, smooth rubber surface for the woven
geotextile and a slightly serrated surface
for the nonwoven geotextile. One of our
customers is using a smooth metal surface.
I am trying to understand what effect a
tongue-and-groove surface might have on
the test results for a woven material. Can you
provide a quick explanation or point me in
the direction of some literature I could read
to understand this better?
FIGURE 2 Improper tongue-and-groove grab
tensile grip faces. Photograph courtesy of GSI
A: Figure 1 shows three grip faces that are
okay to use for the ASTM D4632 and ASTM
D5034 grab test method. However, the grip
faces of Figure 2 are not acceptable. They
are not " flat " as required in section 6.2 of the
ASTM D4632 standard. Such grips have two
effects on the geotextile prior to testing. The
first effect is that they preload the specimen.
Hence, the modulus and elongation values
will be off (the elongation will be less, and
the modulus will be higher). Secondly, the
tongue-and-groove faces use up much more
than 2 inches (50 mm) of material in the
length direction of the grips versus the flat
faces. This leads the strength to be as much
as 10% higher, depending on the severity of
the profile and the type of material tested.
PIPE PENETRATIONS
THROUGH GEOMEMBRANES
>> For more, search Techline at
GeosyntheticsMagazine.com
or email your technical questions
to gmatechline@ifai.com.
Q: Is there a recommended detail that you
can provide or point me toward for pipe
penetrations through geomembrane single
and double liners?
A: You should review American Society
for Testing and Materials (ASTM) D6497
Standard Guide for Mechanical Attachment
of Geomembranes to Penetrations or
Structures. It is excellent, with three triedand-true
standard details that address pipe
penetrations through geomembranes. Please
note, most of the details in the standard
suggest using prefabricated, factorymanufactured
boots for this purpose.
GEOTEXTILE IMPACT TESTING
Q: We would like to carry out an impact
test on geotextiles as described in Koerner
(2012), Chapter 2.3.3 Mechanical PropertiesImpact
Test and Chapter 2.5.5 Impact (Tear)
Resistance. I came across the Geosynthetic
Research Institute (GRI) GS2 Test Method
for Rupture Strength of Geosynthetics by
Pendulum Impact testing standard. My
questions regard the test apparatus that you
are using. Did you purchase this apparatus?
Did you build it?
A: Nice to hear from you, and I hope this
email finds you well. Yes, we built the
apparatus, and we used the following two
American Society for Testing and Materials
(ASTM) impactors.
* ASTM D1922 Standard Test Method for
Propagation Tear Resistance of Plastic Film
and Thin Sheeting by Pendulum Method
* ASTM D5942 Standard Test Method for
Determining Charpy Impact Strength
of Plastics
Both the Elmendorf and Charpy have
modifications with points and holders.
One can buy used equipment on eBay at a
reasonable price. If you want a tutorial on
using these devices, check out the wellwritten
thesis by Monteleone (1986).
You should also be aware that most impact
testing is now done with a falling-weight
device, rather than the pendulum-style
equipment you referenced. I would
recommend that you also consult the
following standards for details about your
experimental design.
* ASTM D1790 Standard Test Method for
Brittleness Temperature of Plastic Sheeting
by Impact
* ASTM D2444 Standard Practice for
Determination of the Impact Resistance of
Thermoplastic Pipe and Fittings by Means
of a Tup (Falling Weight)
* ISO 13433 Geosynthetics-Dynamic
Perforation Test (Cone Drop Test)
Koerner, R. M. (2012). Designing with geosynthetics,
6th ed., Vol. 1. Xlibris, Bloomington, Ind.
Monteleone, M. J. (1986). " Puncture and impact
behavior of various geosynthetics. " MSCE Thesis,
Drexel University, Philadelphia, Pa. G
10
Geosynthetics | June July 2022
http://www.GeosyntheticsMagazine.com

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
Geosynthetics June/July 2022 - 10
Geosynthetics June/July 2022 - 11
Geosynthetics June/July 2022 - 12
Geosynthetics June/July 2022 - 13
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Geosynthetics June/July 2022 - Cover3
Geosynthetics June/July 2022 - Cover4
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