protrusions which could damage the geotextile. Subgrade materials and
compaction requirements shall be in accordance with Section [_____].
3.2.2
Placement
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NOTE: For collection ditches, geotextile placed in
the direction of flow should be wide enough to cover
the entire width of the ditch. If this is not
possible, the geotextile should be placed
perpendicular to the direction of flow and shingled
in the down-gradient direction.
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The Contractor shall notify the Contracting Officer a minimum of 24 hours
prior to installation of geotextile. Geotextile rolls which are damaged or
contain imperfections shall be repaired or replaced as directed. The
geotextile shall be laid flat and smooth so that it is in direct contact
with the subgrade. The geotextile shall also be free of tensile stresses,
folds, and wrinkles. On slopes steeper than 10 horizontal on 1 vertical,
the geotextile shall be laid with the machine direction of the fabric
parallel to the slope direction.
3.3
SEAMS
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NOTE: Overlapped seams are commonly used for
geotextile not placed in tension. Geotextile seams
can also be produced by sewing or the application of
thermal energy. Contact the geotextile manufacturer
for installation instructions using thermal methods.
ASTM D 4886 should be referenced for heat seamed
For geotextile placed in tension, seams should be
sewn and the stitch type should be based on the
manufacturer's recommendations.
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3.3.1
Overlap Seams
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NOTE: Seams are typically overlapped a minimum of
300 mm (12 inches). The specified seam overlap
should be greater than 300 mm (12 inches) for soft
subgrades or where large amounts of differential
settlement are anticipated. The maximum overlap is
typically 1 meter (36 inches). For soils with a CBR
value of less than 1, seams are typically sewn.
Refer to AASHTO M 288 for additional guidance on
overlaps for soft subgrade conditions.
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Geotextile panels shall be continuously overlapped a minimum of [300]
[_____] mm [12] [_____] inches at all longitudinal and transverse joints.
Where seams must be oriented across the slope, the upper panel shall be
lapped over the lower panel. If approved, sewn seams may be used instead
of overlapped seams.
SECTION 02373
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