Geosynthetics October/November 2021 - 40

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By George R. Koerner
New anchorage and connection
strength tests for geosynthetics
onnections can have a significant impact on the performance of exposed geosynthetic
systems. The connection must be considered as a limiting strength factor and evaluated
by the same performance standards as the material alone. If used in critical structures with
design lives of more than 30 years, the geosynthetic and its connections must be evaluated
for limitations, such as ultimate tensile strength. Anchored connections can be secured by
a variety of techniques. The Geosynthetic Institute (GSI) has developed a new test method
that looks at both the mobilized anchor strength in the field and connections in the lab of
exposed geosynthetics as a means of evaluating the factors that affect their performance.
This test has applicability to anchored geosynthetic
systems (AGS), first proposed by
Koerner (1984) for the stabilization of slopes.
AGS provides in situ stabilization of soil slopes
by combining a surface-deployed geosynthetic
with an anchoring system of driven reinforcing
rods or short cable tiebacks. Installation of the
George R. Koerner is the
director of the Geosynthetic
Institute in Folsom, Pa.
system involves tensioning a geosynthetic over a
slope's surface by driving anchors through the geosynthetic
at a given spacing and distance. By tensioning
the geosynthetic over the slope's surface, a
compressive load is applied to the slope. Benefits
of AGS are as follows: (a) increased soil strength
due to soil compression; (b) increased compressive
loading on potential failure surfaces; (c) soil
reinforcement through soil nails or anchors; (d)
halt of soil creep; (e) erosion control; and (f) longterm
soil consolidation. AGS can be used not only
on slopes, but also for canals, channels and levees.
Anchored geosynthetic technology also lends itself well to exposed geomembrane
FIGURE 1 Field anchor pullout test
covers (EGCs). They have been used on landfills in place of more traditional soil-covered
geomembranes since the 1990s (Richardson 2000). The design details and economic
benefits of not using a soil cover have been well documented. While EGCs are temporary,
they do provide improved landfill gas capture; they reduce the amount of stormwater that
infiltrates into the landfill, which creates additional leachate; and they reduce potential
erosion. The lateral expansion mode of operations at most landfills and the creation of
interim slopes that may be exposed for years prior to receiving additional waste present
an opportunity for EGCs that need to be anchored.
Both Giroud et al. (1995) and Wayne and Koerner (1988) emphasize the need for such a
test protocol. It is shocking to see how strong many of our exposed geosynthetics are when
tested in this configuration. Many high-performance turf reinforcement mats (HPTRMs)
(used for AGS) and some reinforced geomembranes (used for EGCs) are stronger than the

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Geosynthetics October/November 2021

Table of Contents for the Digital Edition of Geosynthetics October/November 2021