The great flexibility of these fabrics helps to assure the long-term con-
tinuity of the filter. While all of these fabrics will bend, crease, fold,
and stretch to some degree without rupturing, the relative performance of dif-
ferent proprietary fabrics are quite varied. However, it is important to
properly place the fabric loosely so that distortions that occur from place-
ment of heavy stones will not subject the fabric to stresses beyond its elas-
tic limits and to adequately o v e r l a p adjacent sections to insure continuity.
Over 30 different fabrics for coastal usage are commercially available in
the United States in either woven or nonwoven styles. In any given project
application it is important to consider which of these proprietary fabrics
will best meet the engineering design parameters. Before selection of a par-
ticular geotechnical fabric is made for its applicability to a specific de-
sign, it is important to determine the physical, chemical, and engineering
properties of commercially available filter fabrics with respect to design
criteria. There may be large variations in these properties (see Table) and
the cost can vary greatly.
TABLE
General Properties of Geotechnical Fabrics
ITEM
REMARKS ANDREFERENCES
1.
Weave. . . . . . . . . . . . . . . .Woven, Nonwoven, or Perforated
2.
Thickness. . . . . . . . . . . . . ASTM-D-1777, Dimension of Fibers
3.
Weight . . . . . . . . . . . . . . .ASTM-D-1910, Construction Character-
istics
4.
Breaking Load and Elongation . . . .ASTM-D-1682, Grab and Strip Test
a. Warp Direction (length)
b . Fill Direction (width)
5.
Bursting Strength. . . . . . . . . .ASTM-D-751, Testing of Fabrics
6.
Puncture Test. . . . . . . . . . . ASTM-D-751, Modified
7.
Abrasion Resistance. . . . . . . . .ASTM-D-1175
8.
Abrasion Strength. . . . . . . . . .ASTM-D-1682
9.
Equivalent Opening Size (EOS). . . .Care should be used to prevent clog-
(US Sieve No. Equivalent)
ging by sediment or loss of fines
through the fabric.
10.
Elastic Properties . . . . . . . . .ASTM-D-1774
11.
-Water Permeability . . . . . . . . .Gradient-Ratio should not exceed 3
(see Guide Specifications, OCE, 1977)
12.
Chemical Composition . . . . . . . .Fiber material could be: nylon,
polypropylene, polyamide, polyester,
olefine, fiber glass, etc.
13.
Accelerated Aging. . . . . . . . . .Some deterioration after prolonged
exposure to sunlight if not buried
in structure. (See Fed. Stnd. 191.)
Guidelines for quality control can be found in the following reference:
U.S. ARMY, CORPS OF ENGINEERS, "Plastic Filter Cloth," Guide Specifications
CW-02215, Office of the Chief of Engineers, Washington, DC, November, 1977.
2
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