Special smoothness tolerances are not required for
subgrades for railroads; therefore, both sets of
brackets will be removed when writing specifications
for preparation of railroad subgrade only. When
writing specifications for preparation of roadway
and/or airfield pavement subgrade, the brackets will
be removed from the applicable sentences and the
smoothness tolerances showing permissible deviations
in fractions of a millimeter (inch) and the length
of straightedge in meters (feet) will be inserted in
the blanks as appropriate.
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Subgrade shall be shaped to line, grade, and cross section, and compacted
as specified. This operation shall include plowing, disking, and any
moistening or aerating required to obtain specified compaction. Soft or
otherwise unsatisfactory material shall be removed and replaced with
satisfactory excavated material or other approved material as directed.
Rock encountered in the cut section shall be excavated to a depth of 150 mm
6 inches below finished grade for the subgrade. Low areas resulting from
removal of unsatisfactory material or excavation of rock shall be brought
up to required grade with satisfactory materials, and the entire subgrade
shall be shaped to line, grade, and cross section and compacted as
specified. [After rolling, the surface of the subgrade for roadways shall
not show deviations greater than [_____] mm inch when tested with a [_____]
meter foot straightedge applied both parallel and at right angles to the
centerline of the area.] [After rolling, the surface of the subgrade for
airfields shall not show deviations greater than [_____] mm inch when
tested with a [_____] meter foot straightedge applied both parallel and at
right angles to the centerline of the area.] The elevation of the finish
subgrade shall not vary more than 15 mm 0.05 foot from the established
grade and cross section.
3.14.3
Compaction
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NOTE: Use 90% of ASTM D 698 or ASTM D 1557 for
General Site Compaction of cohesionless materials on
Army projects and 85% of same for Navy projects.
For Army projects see TM 5-818-1, TM 5-818-7, TM
5-825-2 and DM 21.3 for criteria and design
guidelines. Specify most jobs using ASTM D 698
compaction, except for roads, airfields, and other
heavily loaded areas, which should use ASTM D 1557
compaction. Specify compaction in terms of one
compaction effort (ASTM D 698 or ASTM D 1557), if
possible.
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Compaction shall be accomplished by sheepsfoot rollers, pneumatic-tired
rollers, steel-wheeled rollers, vibratory compactors, or other approved
equipment. Except for paved areas and railroads, each layer of the
embankment shall be compacted to at least [_____] percent of laboratory
maximum density.
3.14.3.1
Subgrade for Railroads
Subgrade for railroads shall be compacted to at least 90 percent laboratory
maximum density for cohesive materials or 95 percent laboratory maximum
SECTION 02300
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