Geosynthetics October/November 2023 - 10

Q &
CRIMPING PREFABRICATED
VERTICAL DRAINS
Q: Can you enlighten me of any work related
to the crimping of prefabricated vertical drains
(PVD) as a result of soil consolidation and
settlement of harbor sludge or dredge spoil?
We are anticipating 3 feet (1 m) of settlement
in 30 feet (10 m) of sediment (sludge/spoil).
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A: I would recommend the following two
papers on the subject:
Cortlever N.G. (1983). " Investigation into the
behavior of plastic drains in Rotterdam Harbour
sludge. " Geotechnics Holland BV) 1-16.
Lawrence, C. A., and Koerner, R. M. (1988).
" Flow behavior of kinked strip drains. " Proc.,
Geosynthetics for Improvement, New York,
ASCE, 22-39.
Your 10% total strain is not worrisome. If you
go above 25% localized strain, things get
interesting for some PVDs. The core could
break, and then transmissivity would be
drastically reduced.
Please check out the ASTM standards available
for PVD. The pertinent ones are as follows:
ASTM D6917 Standard Guide for Selection
of Test Methods for Prefabricated Vertical
Drains PVD
ASTM D6918 Standard Test Method for
Testing Vertical Strip Drains in the Crimped
Condition ASTM D7498 Standard Test
Method for Vertical Strip Drains Using
a Large Scale Consolidation Test
10
Geosynthetics | October November 2023
A
GMA TECHLINE
MODERATED BY
George R. Koerner
GEOTEXTILES TRACEABILITY
Q: We are having a problem with traceability
on our project with geotextiles. Does this
really matter for each roll and lot of material?
A: Yes, it does. The labels must match
inside and outside of the product. Insist
that the geotextile itself is branded and
conforms to ASTM D4873 Standard Guide
for Identification, Storage and Handling
of Geosynthetic Rolls and Samples. It
is easy for an unethical distributor to
rewrap and change the identification on a
substandard geotextile roll if it is not labeled
or branded correctly. Please have a look at
the American Association of State Highway
and Transportation Officials (AASHTO)
Product Evaluation and Audit Solutions
(formerly National Transportation Product
Evaluation Program [NTPEP]) requirements
for geotextiles). They are summarized below
and are believed to be effective at acquiring
preapproved quality geotextiles.
* The program is voluntary and open to all
(i.e., domestic and international vendors).
* Both private labelers and prime supplier(s)
go through a compliance check and an onsite
audit every three years prior to having
materials placed on the AASHTO Product
Evaluation and Audit Solutions approved list.
* All prime manufacturers are required to
print a unique identification code (given
by AASHTO-Product Evaluation and Audit
Solutions) every 16 feet (5 m) on each of
their approved products.
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Geosynthetics October/November 2023

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