Geosynthetics April/May 2024 - 12

Q &
GEOSYNTHETICS FOR
MARINE STRUCTURES
Q: Are geosynthetics allowed to be used in
marine structures? I am concerned about plastics
in the environment and emission of plastic
additives and their degradation by-products.
THE GEOSYNTHETIC
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A: Geosynthetics have provided a wide
range of solutions for many types of marine
structures including revetments, levees,
jetties, breakwaters and offshore structures
for the past 40 years. Geosynthetics are longterm,
durable polymers that are made to
withstand environmental conditions. They
are not single-use plastics, which produce
debris. However, geosynthetics don't last
forever. They will age and degrade over
time. Hence, all marine structures built with
geosynthetics should be monitored and
maintained according to a plan. One needs
to assign a half-life to all geosynthetics and
define property thresholds that forecast an
appropriate reconstruction schedule.
The degradation by-product strongly depends
on the geosynthetic's polymer formulation and
fabrication. For example, a properly stabilized
submerged polypropylene geotextile, where
the supply of oxygen is limited and the
temperature is low, can last 100-plus years.
However, some products will fail within a few
decades under these same conditions if they
were poorly formulated or carelessly fabricated
and installed. The same reasoning applies to
the environmental impacts of the emission
of additives. The loss of additives is directly
related to the aging of the geosynthetic.
12
Geosynthetics | April May 2024
A
GMA TECHLINE
MODERATED BY
George R. Koerner
GEOTEXTILE QUALITY ISSUES
Q: We are performing certified quality
auditing (CQA) at a jobsite and having major
quality issues with the geotextile delivered
to the site. For example, the mass per unit
area is low, all mechanical properties are
below specification, the permittivity and
apparent opening size (AOS) are low. We
are afraid to check the endurance property
requirements for the project, which is a
geotextile filter below riprap on a slope
within a tidal basin. Can you suggest how
we can reconcile this issue?
A: I hope you have good plans and
specifications in place. If so, hold true to
the task and reject the material. There is
an owner and the general public counting
on you. In addition, this is not some
casual application with mundane (i.e.,
straightforward) boundary conditions. This
application has reversing flow, the possibility
of biological and chemical (precipitation)
clogging, installation damage concerns and
probably a design life of greater than 50
years. In short, a designer spent a lot of time
and effort specifying this material. You need
to stand strong, even though it is going to
be inconvenient and cost much time and
money. P.S. Document everything.
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Geosynthetics April/May 2024

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