TM 5-818-8/AFJMAN 32-1030
1
Minimum Requirement
Test Method
Property
(1)
(2)
(3)
Weight', ounce per square yard
15
ASTM D 3776
option B
--
Needle-punched nonwoven
Structure
Grab tensile strength, pounds
350
ASTM D 4632
Elongation at failure, percent
ASTM D 4632
20
620
ASTM D 3786
Burst strength, pounds per
square inch
185
ASTM D 4833
Puncture strength, pounds
Trapezoidal tear strength, pounds
150
ASTM D 4533
ASTM D 4751
Apparent opening size (AOS),
<0.22
(No. 70 sieve)
millimeter
ASTM D 4491
0.1
Normal permeability,
, centimeters
per second
ASTM D 4491
Permittivity, seconds
0.2
4
6
ASTM D 4716
Planar water flow/transmissivity
-3
square feet per minute X 10
Ultraviolet degradation at 150 hours
70
ASTM D 4355
percent strength retained
5
ASTM D 1683
Seam strength, pounds
350
Value in weaker principal direction. All numerical values represent minimum
average roll value.
2
The minimum weight listed herein is based on the experience that geotextiles
with weights less than 15 oz/yd tend to show greater abrasion and wear than do
heavier weight materials.
It is recommended that the selection of geotextile
be based on the minimum physical property requirements of this table and not
solely on weight.
3
The k of the geotextile should be at least five times greater than the k
value of the soil.
4
Planar water flow/transmissivity determined at normal stress of 3.5 psi and
i = 1.0.
5
Seam strength applies to both field and manufactured seams, if geotextile is
seamed.
Table 5-1. Recommended Geotextile Property Requirements for Railroad Applications.
5-5. Protective Sand layer
subgrade bearing pressure. In the design of new
a. Although not normally required, a 2-inch-
track construction or track rehabilitation using
thick layer placed over the geotextile may assist in
geotextiles, the geotextile should be placed at the
reducing the abrasion forces caused by the ballast
deeper of the following:
as well as provide an additional filtration layer. In
a. At least 12 inches below the cross tie.
track rehabilitation where undercutting or plow-
b. At the bottom of the ballast layer in the case
ing type of ballast removal operation is used, there
of rehabilitation by plowing.
may be many large aggregate pieces remaining on
c. At the bottom of the subballast in new con-
the surface of the subgrade prior to the placement
of the geotextile. A 2-inch-thick layer of sand
struction or rehabilitation where the track is
removed.
placed on the subgrade provides a smooth surface
5-2
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