materials or 95 percent laboratory maximum density for cohesionless
materials to prevent wedging action or eccentric loading upon or against
the structure. Ground surface on which backfill is to be placed shall be
prepared as specified in paragraph PREPARATION OF GROUND SURFACE FOR
EMBANKMENTS. Compaction requirements for backfill materials shall also
conform to the applicable portions of paragraphs PREPARATION OF GROUND
SURFACE FOR EMBANKMENTS, EMBANKMENTS, and SUBGRADE PREPARATION, and Section
02630 STORM DRAINAGE; and Section 02300 EARTHWORK. Compaction shall be
accomplished by sheepsfoot rollers, pneumatic-tired rollers, steel-wheeled
rollers, vibratory compactors, or other approved equipment.
3.11.1
Trench Backfill
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NOTE: Most pressure tests require backfilling to at
least 600 mm (2 feet) over the pipe with the joints
and couplings left open for inspection.
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Trenches shall be backfilled to the grade shown. [The trench shall be
backfilled to [_____] meters feet above the top of pipe prior to performing
the required pressure tests. The joints and couplings shall be left
uncovered during the pressure test.] [The trench shall not be backfilled
until all specified tests are performed.]
3.11.1.1
Replacement of Unyielding Material
Unyielding material removed from the bottom of the trench shall be replaced
with select granular material or initial backfill material.
3.11.1.2
Replacement of Unstable Material
Unstable material removed from the bottom of the trench or excavation shall
be replaced with select granular material placed in layers not exceeding
150 mm 6 inches loose thickness.
3.11.1.3
Bedding and Initial Backfill
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NOTE: Bedding is provided to level out any
irregularities in the foundation and to assure
uniform support along the barrel of each pipe
section. Bedding is also constructed to distribute
the load bearing reaction, due to the weight of the
backfill material, around the lower portion of the
pipe. If the pipe or conduit is placed directly on
a flat or shaped foundation, delete "bedding" from
the title and from any reference in the paragraph.
If bedding will be specified, determine type and
thickness and show on the plans. Specify compaction
to 95 percent maximum density for cohesionless
soils, and 90 percent maximum density for cohesive
soils.
Any locally available fine aggregate for concrete or
asphalt mixtures will qualify as sand and may be
specified by local gradation and specification
number in lieu of "SW" or "SP." Drawings (details)
should clearly show where sand backfill or bedding
SECTION 02300
Page 33
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