Geosynthetics October/November 2021 - 9

REPEATABILITY AND REPRODUCIBILITY
Q: If repeatability and reproducibility are high,
it is a positive output, but high repeatability and
reproducibility will give high uncertainty from
Equation 1:
uncertainty = sqrt (repeatability^2 +
reproducibility^2)
Could you explain to me why it looks like it
is contradictory?
A: One wishes to have the repeatability and
reproducibility as " low " as possible, hopefully in
single digits for well-behaved tests on consistent
materials. With this in mind, the uncertainty
will be low. Please note that the uncertainty in
the test result is not used to approve or reject
a product on-site. However, questions will be
raised if the uncertainty for a test is high and the
test result does not meet the specification values
within a few percentage points of the target. In
some cases, owners and construction quality
assurance (CQA) inspectors are considering a
tolerance or range for acceptance.
(1)
MEASURING STRAIN IN GEOSYNTHETICS
Q: Currently, what is the best-known method to
measure strains in geosynthetics? We are having
arguments between results generated from
crosshead movement and extensometers.
A: This question arises often when comparing
ISO 527/ASTM D638 and ASTM D6693 results. The
former requires an extensometer, where the latter
utilizes crosshead deflection and assumes gauge
lengths. This discussion first needs to start with
preload on the specimen and the assurance that
there is no slack in the specimen at the start of
the test. The next point is that the extensometers
are generally set up with a gauge length of 1 inch
(25 mm), where ASTM D6693 assigns a gauge
length for yield at 1.3 inches (33 mm). Therefore,
the elongation (strain) at yield is rarely going
to be comparable. In short, the strain for highdensity
polyethylene (HDPE) geomembranes will
be in the low teens for ISO 527/ASTM D638 and
in the high teens for ASTM D6693. This infuriates
people who oversee specification review but is
an artifact of the testing procedure.
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Geosynthetics October/November 2021

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

Geosynthetics October/November 2021 - Cover1
Geosynthetics October/November 2021 - Cover2
Geosynthetics October/November 2021 - 1
Geosynthetics October/November 2021 - 2
Geosynthetics October/November 2021 - 3
Geosynthetics October/November 2021 - 4
Geosynthetics October/November 2021 - 5
Geosynthetics October/November 2021 - 6
Geosynthetics October/November 2021 - 7
Geosynthetics October/November 2021 - 8
Geosynthetics October/November 2021 - 9
Geosynthetics October/November 2021 - 10
Geosynthetics October/November 2021 - 11
Geosynthetics October/November 2021 - 12
Geosynthetics October/November 2021 - 13
Geosynthetics October/November 2021 - 14
Geosynthetics October/November 2021 - 15
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Geosynthetics October/November 2021 - 18
Geosynthetics October/November 2021 - 19
Geosynthetics October/November 2021 - 20
Geosynthetics October/November 2021 - 21
Geosynthetics October/November 2021 - 22
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Geosynthetics October/November 2021 - 24
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Geosynthetics October/November 2021 - 27
Geosynthetics October/November 2021 - 28
Geosynthetics October/November 2021 - 29
Geosynthetics October/November 2021 - 30
Geosynthetics October/November 2021 - 31
Geosynthetics October/November 2021 - 32
Geosynthetics October/November 2021 - 33
Geosynthetics October/November 2021 - 34
Geosynthetics October/November 2021 - 35
Geosynthetics October/November 2021 - 36
Geosynthetics October/November 2021 - 37
Geosynthetics October/November 2021 - 38
Geosynthetics October/November 2021 - 39
Geosynthetics October/November 2021 - 40
Geosynthetics October/November 2021 - 41
Geosynthetics October/November 2021 - 42
Geosynthetics October/November 2021 - 43
Geosynthetics October/November 2021 - 44
Geosynthetics October/November 2021 - Cover3
Geosynthetics October/November 2021 - Cover4
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-december-2021-january-2022
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-october-november-2021
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-august-september-2021
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-june-july-2021
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-april-may-2021
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-february-march-2021
https://www.nxtbook.com/ifai/geosynthetics/1220GS
https://www.nxtbook.com/ifai/geosynthetics/1020GS
https://www.nxtbook.com/ifai/geosynthetics/0820GS
https://www.nxtbook.com/ifai/geosynthetics/0620GS
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https://www.nxtbook.com/ifai/geosynthetics/1019GS
https://www.nxtbook.com/ifai/geosynthetics/0819GS
https://www.nxtbook.com/ifai/geosynthetics/0619GS
https://www.nxtbook.com/ifai/geosynthetics/0419GS
https://www.nxtbook.com/ifai/geosynthetics/0219GS
https://www.nxtbook.com/ifai/geosynthetics/1218GS
https://www.nxtbook.com/ifai/geosynthetics/1018GS
https://www.nxtbook.com/ifai/geosynthetics/0818GS
https://www.nxtbook.com/ifai/geosynthetics/0618GS
https://www.nxtbook.com/ifai/geosynthetics/0418GS
https://www.nxtbook.com/ifai/geosynthetics/0218GS
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