Geosynthetics February/March 2022 - 42

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By George R. Koerner
Will a reinforced levee induce
a seepage path adjacent to and
around geogrid layers?
T
he Geosynthetic Institute (GSI) has been asked if a geogrid-reinforced levee will induce
a seepage path adjacent to and around the geosynthetic layers. This question has been
asked on several occasions for different applications and various styles of geogrids. At this
point, GSI has no case histories where it can quantify such
behavior. Geogrids are critical reinforcing elements in existing
levees (Figure 1). The significance of this work, with the
aid of geosynthetics in the core section, is amplified because
of the frenetic pace of heightening levees due to sea level rise
(a result of global warming).
Our first foray into quantifying this phenomenon surGeorge
R. Koerner, Ph.D.,
P.E., CQA, is the director of
the Geosynthetic Institute
in Folsom, Pa.
rounded work with a modified ASTM D5887 " Standard Test
Method for Measurement of Index Flux Through Saturated
Geosynthetic Clay Liner Specimens Using a Flexible Wall
Permeameter " device. We know from Daniel, Bowders and
Gilbert (1997) that hydraulic-conductivity testing using
flexible-wall cells is usually preferred over rigid-wall cells due
to the potential for sidewall leakage problems with rigid-wall
cells. Excessive sidewall leakage may occur, for example, when
test soil shrinks during permeation. Also, the use of a rigidwall
cell does not allow for control of the effective stresses
that exist in the test specimen. In addition, particles lining up
on a rigid boundary may lead to a preferential path, rather
than the tortuous one through the center of the soil portion
of the specimen.
GSI incorporated geogrids (punched and drawn, strap type
and woven coated) into the center of 4-inch (100-mm) cylindrical
soil (SC, CL-ML and CH) permeability samples (Figures
FIGURE 2a Preparing geogridsoil
permeability specimen
Will a Reinforced Levee Induce a Seepage Path Adjacent to and Around Geogrid Layers?
George R. Koerner Ph.D., PE & CQA, Director Geosynthetic Institute Folsom, PA USA
We have been asked if a geogrid reinforced levee will induce a seepage path adjacent to and
around the geosynthetic layers. This question has been asked on several occasions for different
applications and styles of geogrids. At this point, we have no case histories where we can
quantify such behavior. As seen in Figure 1, geogrids are critical reinforcing elements in
existing levees. The significance of this work, with the aid of geosynthetics in the core section,
is amplified because of the frenetic pace of heightening levees due to sea level rise (a result of
global warming).
FIGURE 2b Disassembled specimen
after permeability testing
FIGURE 1 Reinforced dike expansion over existing levee using geosynthetics
Figure 1- Reinforced dike expansion over existing levee utilizing geosynthetics
Our first foray into trying to quantify this phenomenon surrounded work with a modified ASTM
D5887 " Standard Test Method for Measurement of Index Flux Through Saturated Geosynthetic
Clay Liner Specimens Using a Flexible Wall Permeameter " device We know from Daniel D E

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Geosynthetics February/March 2022

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