Geosynthetics August/September 2020 - 10

THE

GMA TECHLINE

answers all
Moderated by George R. Koerner

BUILDING FROM THE BOTTOM UP
Q: I am currently detailing a 45° reinforced
slope for a highway overpass (26 feet [8 m]
high). We have designed this without a facing
system to allow the contractor to overfill and
then trim back to the design profile.
I have not personally seen this done, but
standards and text suggest it to be practical.
Do you have any examples of this being
successful and what provisions are worth
considering for protection of the grid during
the subsequent trimming operation?
Thanks in advance.
A: If you are detailing (i.e., building) a 45˚
(1:1) reinforced 26-foot highway slope, why
wouldn't you build it to grade (use GPS or
lidar survey to assure location of geosynthetic
reinforcement) with a long track hoe, gradall
or stone slinger (conveyor)? Build from the
bottom up after you set (backfill) the anchor
trench or plinth.
Please, do not overbuild the toe and cut with
a dozer as you suggest. I have seen this done
on glacial tills and CCL for landfill liners of 2:1
slopes (26.5˚), not 1:1 slopes (45˚). For health
and safety concerns, please be very careful
with that approach.
You may want to use "L" frame wire mesh face
supports, prebuild facings units or a twopronged compaction approach to facilitate
construction. All are tried and true techniques
used for building geosynthetic-reinforced
green walls.

10

REQUIRED DEGREE
OF SURVIVABILITY
Q: I am working as a quality assurance/quality
control (QA/QC) engineer for infra projects.
I had many discussions with our project
consultant regarding all parameters required
for the geotextile, precisely, the nonwoven
used for road and trenches.
I believe that every project was guided by its
project specs and the country specs, but really,
I had some point that I need some clarification
on it. Specifically, for the nonwoven and
the use on the infra project, which class is
advised? What are the critical parameters and
what are the performance parameters? Burst
strength: is it required for a geotextile?
Based on my experience, for every test we
should think about its purpose, and then we
will decide technically if it complies or not.
A: Thank you for your GMA Techline question
in regard to geotextile survivability.
Please consult Table 3 of GRI-GT13a for the
required degree of survivability based on
ground pressure of construction equipment
and subgrade conditions. Geotextiles
are typically tested for three survivability
parameters: ASTM D4632 Grab, ASTM D4533
Trapezoidal Tear and ASTM D6241 CBR
Puncture. Burst is no longer specified due
to test variability.

Geosynthetics | August September 2020

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7/22/20 11:21 PM



Geosynthetics August/September 2020

Table of Contents for the Digital Edition of Geosynthetics August/September 2020

Geosynthetics August/September 2020 - Cover1
Geosynthetics August/September 2020 - Cover2
Geosynthetics August/September 2020 - 1
Geosynthetics August/September 2020 - 2
Geosynthetics August/September 2020 - 3
Geosynthetics August/September 2020 - 4
Geosynthetics August/September 2020 - 5
Geosynthetics August/September 2020 - 6
Geosynthetics August/September 2020 - 7
Geosynthetics August/September 2020 - 8
Geosynthetics August/September 2020 - 9
Geosynthetics August/September 2020 - 10
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Geosynthetics August/September 2020 - 35
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Geosynthetics August/September 2020 - 41
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Geosynthetics August/September 2020 - 45
Geosynthetics August/September 2020 - 46
Geosynthetics August/September 2020 - 47
Geosynthetics August/September 2020 - 48
Geosynthetics August/September 2020 - Cover3
Geosynthetics August/September 2020 - Cover4
https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-december-2021-january-2022
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