Section 4196. Engineering Fabrics
A. Meet the following requirements for engineering fabrics (known as geotextiles):
1. Permeable, synthetic textile materials suitable for use with soil, rock, or other geotechnical engineering related materials as an integral part of a highway project, structure, or system.
2. Mildew, rot, insect, and rodent resistant.
3. Inert to commonly encountered chemicals found in soil.
4. During all periods of shipment and storage, the fabric is maintained by wrapping in a heavy duty protective covering to protect the fabric from direct sunlight, ultraviolet rays, mud, dirt, dust, and debris.
5. Free of defects or flaws which significantly affect its physical properties.
B. Comply with Materials I.M. 496.01 for inspection and acceptance of engineering fabrics. Label each roll of fabric in a shipment with a number or symbol to identify the production run. Meet the following additional fabric requirements for the specific applications:
1. Silt Fencing.
a. Meet the following requirements:
1) Woven material with a minimum width of 36 inches.
2) Top edge of the fabric hemmed or modified otherwise so that a braided cord or woven belt can be suitably attached for loop tying to fence posts.
3) The cord or belt of minimum tensile strength of 150 pounds.
4) Fabric and any reinforcing plastic netting contains or is treated with ultraviolet stabilizers, sufficient to prevent damaging deterioration for 2 years of outdoor exposure.
5) Has the properties listed in Table 4196.01-1.
b. The fabric may be reinforced with plastic netting of nominal 3/4 inch strand spacing and a minimum three strand grab strength of 40 pounds and 15 pounds after the same accelerated weathering as required for the fabric. Fabric that is reinforced in this manner may have lower grab strengths as indicated.
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Table 4196.01-1: Silt Fencing Fabric Properties |
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Property |
Value |
Test Method No. |
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Grab Strength, dry, minimum average fill direction run direction(a) |
100 lbs. 150 lbs. |
ASTM D 4632 |
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Ultraviolet Stability (Retained Strength) |
70% |
ASTM D 4355 |
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Permittivity |
0.05 |
ASTM D 4491 |
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Apparent Opening Size, maximum |
US Sieve No. 30 |
ASTM D 4751 |
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(a) When plastic net reinforcing is used, ensure the minimum average grab strength requirement for fabric, before and after accelerated weathering, is 100 pounds and 35 pounds, respectively. Apply the grab strength to both the fill and run direction. |
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2. Subsurface Drainage.
In subsurface drains, use fabric that:
· Is capable of withstanding normal installation stresses, and
· Has the properties listed in Table 4196.01-2.
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Table 4196.01-2: Fabric for use in Subsurface Drains |
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Property |
Value |
Test Method |
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Grab strength, dry, minimum average value in either principal direction |
90 lbs. |
ASTM D 4632 |
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Elongation, dry, minimum average value in either principal direction |
20% |
ASTM D 4632 |
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Permittivity, minimum |
0.1 sec-1 |
ASTM D 4491 |
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Apparent Opening Size, maximum |
US Sieve No. 40 |
ASTM D 4751 |
3. Embankment Erosion Control.
Under concrete and stone revetment, erosion stone, or gabions used for embankment erosion control, use fabric that:
· Is capable of withstanding normal installation stresses, and
· Has the properties listed in Table 4196.01-3.
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Table 4196.01-3: Fabric for use as Embankment Erosion Control |
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Property |
Value |
Test Method |
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Grab strength, dry, minimum average value in either principal direction |
150 lbs. |
ASTM D 4632 |
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Elongation, dry, minimum average value in either principal direction |
20% |
ASTM D 4632 |
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Permittivity, minimum |
0.1 sec-1 |
ASTM D 4491 |
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Apparent Opening Size, maximum |
US Sieve No. 40 |
ASTM D 4751 |
4. Asphalt Overlay Fabric.
a. When placing fabric under asphalt mixtures to provide waterproofing and delay reflective cracking, ensure the fabric:
· Is capable of withstanding installation stresses,
· Is not damaged by temperatures common to asphalt mixtures, and
· Has the properties listed in Table 4196.01-4.
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Table 4196.01-4: Fabric Placed under Asphalt Mixtures |
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Property |
Value |
Test Method |
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Grab strength, dry, minimum average value in either principal direction |
90 lbs. |
ASTM D 4632 |
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Elongation, dry, minimum average value in either principal direction |
20% |
ASTM D 4632 |
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Grab Strength after 400°F for 3 hr.(a) minimum average value in either principal direction |
75 lbs. |
ASTM D 4632 |
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(a) Applies only when asphalt temperatures exceeding 300°F are anticipated. |
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b. Ensure asphalt absorption is sufficient to produce a good bond between the overlay and the overlaid surface when a tack coat of 0.20 gallon to 0.25 gallon of asphalt binder per square yard is used.
c. The Engineer may approve fabrics, such as fiberglass, which do not lend themselves to testing by some of the previously specified methods.
5. Subgrade Stabilization Material.
a. To stabilize a subgrade under pavement or pavement patches, use material that:
· Is capable of withstanding installation stresses, and
· Has the properties listed in Table 4196.01-5a or 4196.01-5b.
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Table 4196.01-5a: Fabric for use as Subgrade Stabilization (Biaxial Polymer Grid) |
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Property |
Value |
Test Method |
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Minimum tensile strength at 2% strain. Both directions. |
250 lbs./ft. |
ASTM D 6637 |
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Aperture size. Both directions. |
0.5 to 2 in. |
Internal Dimension Measuring Calipers |
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Minimum Ultimate junction strength. Both directions. |
790 lbs./ft. |
GRI Test Method GG2 or ASTM D 7737 |
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Table 4196.01-5b: Fabric for use as Subgrade Stabilization (Triaxial Polymer Grid) |
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Property |
Value |
Test Method |
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Minimum radial stiffness at 0.5% strain or Minimum tensile modulus at 2% strain |
13,700 lbs./ft. or 12,000 lbs./ft. |
ASTM D 6637 |
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Minimum isotropic stiffness ratio |
0.60 |
ASTM D 6637 (a) |
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Aperture size. |
0.5 to 2 in. |
Internal Dimension Measuring Calipers |
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Minimum junction efficiency |
90% |
ASTM D 6637/D 7737 |
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(a) Ratio between minimum and maximum values of radial stiffness at 0.5% strain, measured on rib and midway between rib directions. |
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b. Inspection and acceptance of polymer grid will be according to Materials I.M. 496.01.
6. Bridge Abutment Backfill Fabric.
Use engineering fabric having properties listed in Table 4196.01-6.
Table 4196.01-6: Fabric for use in bridge abutment backfill
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Property |
Value |
Test Method |
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Tensile Strength (at 5% Strain), minimum |
1356 lbs/ft |
ASTM D 4595 |
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Apparent opening size (AOS), maximum |
US Sieve No. 40 |
ASTM D 4751 |
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UV resistance (at 500 hours) |
70% retained strength |
ASTM D 4355 |
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Flow Rate, minimum |
10 gal./min./ft2 |
ASTM D 4491 |