Effect of Strain Rate on Tensile Testing of Geogrid
Reinforcements Using Single-Rib and Wide-Rib Specimen
R. HEGAZY, G. M. MAHMOUD, EBTISAM H. HASAN
National Institute for standards (NIS), Tersa street, Haram, Giza, Egypt
Correspondence to: R. Hegazy; e-mail: firstname.lastname@example.org.
Received: March 1, 2016
Accepted: September 7, 2016
A geogrid is geosynthetic high-density polyethylene material used to reinforce soils and similar materials. It is
valuable tool in transportation and civil construction. Geogrids allow engineers to build where it otherwise would not be possible
or would be cost prohibitive using traditional methods. The tensile test of the geogrid is the most important test of this product.
ISO 10319 “Geosynthetics-Wide-Width tensile test” uses wide-width specimen 20 mm wide; the gripping of this wide sample is
difﬁcult and need special gripping. This study aims to develop and validate a method for testing single-rib specimen, instead of
wide specimen using 150 samples of geogrids, and six different speeds. The statistical analysis of the results showed that testing of
single rib at the speed of 100 mm/min (method under validation) gave matched and compatible results of wide-rib specimen test-
ing at the speed of 25 mm/min (reference method), where the variance value of these two methods is not signiﬁcant. © 2016 Wiley
Periodicals, Inc. Adv Polym Technol 2018, 37, 21778; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21778
Geogrid, Method validation, Single rib, Tensile strength, Wide rib
eogrid is a geosynthetic high-density polyethylene mate-
rial with relatively high tensile strength and is a struc-
ture of knitted bands forming grid pattern with large spaces
between the knitted bands as shown in Fig. 1. The knitted
bands and spaces between them provide the high tensile
strength and stabilize them to the projects they are used.
Geogrid is used to reinforce soils and retaining walls, as
well as subbases or subsoils below roads or structures. Soils
pull apart under tension, but geogrids are strong in tension in
comparison with the soil, which allows force transfer to the
soil with large area.
Geogrids are commonly made of polymer materials, such as
polyester, polyethylene, or polypropylene. There are three meth-
ods for the production of geogrids woven from yarns, heat-
welded from strips of material, or punching a regular pattern of
holes in sheets of material, and then stretched into a grid.
Currently, there are three categories of geogrids. The ﬁrst,
and original, called punched and drawn geogrids were
invented by Dr Frank Brian Mercer in the United Kingdom at
Netlon Ltd. (Blackburn, United kingdom) and were brought
in 1982 to North America by the Tensar Corporation, the
another same drawn type geogrid manufactured in Italy by
Tenax, and now products by new manufacturers in Asia.
The second category of geogrids is textile geogrids, which
are manufactured using bundles of polyethylene-coated polye-
ster ﬁbers as the reinforcing component. This led to the
development of polyester yarn geogrids made on textile weav-
ing machinery. In the manufacturing process, many hundreds
of ﬁbers are connected to form longitudinal and transverse
yarn ribs with large voids between them. This type of geogrid
is manufactured by many companies having various trade-
mark products. There are about 25 companies that can manu-
facture coated yarn-type polyester geogrids on the worldwide.
The third category of geogrids is made by laser or ultrason-
ically bonding together polyester or polypropylene rods or
bundle in a grid pattern. Two manufacturers currently make
used polypropylene dumbbell-shaped tensile test
samples. Tensile tests were carried out at various speeds. The
machine used was Zwick Z10 (Ulm, Germany), screw-driven
universal tensile/compression testing machine, with 50-mm/
min test speed. A wide range of speeds from 1 to 1000 mm/
min was used to determine the effect of strain rate. An exten-
someter was used to determine the elastic modules. Tests
were carried out at a temperature of 23°C. The results are
shown in Fig. 2.
The testing of wide-width specimen is more difﬁcult than
single-rib specimen and needs high accuracy, and will ﬁnished
special gripping (recommended roller gripping) to assure the
uniform distribution of load on the specimen as shown in Fig. 3.
The maximum tensile load in a layer (T
) is multiplied
by a minimum speciﬁed factor of safety (F) for each limit state
to compute the design tensile load (T
= F 9 T
). The min-
imum factor of safety is F = 1 and 1.5 for tensile rupture
Advances in Polymer Technology, Vol. 37, No. 4, 2018, DOI 10.1002/adv.21778
© 2016 Wiley Periodicals, Inc.
21778 (1 of 8)