UFC 3-270-04
15 March 2001
where: apparent opening size is a property that indicates the approximate largest particle that will
effectively pass through the geotextile.
For woven geotextiles, the open area of the cloth should not be less than 4 percent or greater
than 36 percent. Where these criteria are met, the criteria given for perforated pipe or screens
are no longer applicable. Where geotextiles are used to line the drainage trench, the following
criteria should be followed:
12.5.3.3. Geotextile adjacent to granular materials containing 50 percent or less by weight of
fines (minus NO. 200 materials):
d85 percent size of the material (mm)
12.5.3.3.1.
>1
Apparent opening size (AOS)(mm)
12.5.3.3.2. Gradient ratio < 3
12.5.3.3.3. For woven geotextiles, open area of the cloth should not be less than 4 percent or
greater than 36 percent.
12.5.3.4. Geotextile adjacent to all other types of soil:
12.5.3.4.1. AOS no larger than the opening in the U.S. Standard Sieve No. 70
12.5.3.4.2. Gradient ratio < 3
12.5.3.4.3. For woven geotextiles, open area of the cloth should not be less than 4 percent or
greater than 10 percent.
Where these criteria are met, the criteria for stability and permeability are no longer applicable,
and the backfill may be selected based on the criteria for perforated pipe or screens. To reduce
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