TM 5-818-8/AFJMAN 32-1030
TRENCH EXCAVATED AND
BEDDING (USUALLY 6-INCH
GEOTEXTILE PLACED TO
MINIMUM) AND COLLECTOR
INSURE INTIMATE CONTACT
PIPE PLACED (IF PIPE IS
WITH SOIL SURFACES AND
REQUIRED)
THAT PROPER OVERLAP WILL
BE AVAILABLE AFTER BACK-
FILLING
REMAINDER OF BACKFILL
GEOTEXTILE SECURELY OVER-
PLACED AND COMPACTED AS
LAPPED (USUALLY 12-INCH
REQUIRED TO PRODUCE COM-
MINIMUM) ABOVE BACKFILL
PATIBLE STRENGTH AND
SO SOIL INFILTRATION IS
CONSOLIDATION WITH SUR-
PREVENTED. COVER MATE-
ROUNDING SOIL AND STRUCTURES
RIAL PLACED AND COMPACTED
Figure 3-1. Trench Drain Construction.
as a cover for the pipe perforations preventing
in engineered applications, this method is less
backfill infiltration. If the geotextile can be sepa-
efficient than lining the trench with a geotextile
rated a small distance from the pipe surface, the
because the reduced area of high permeability
flow through the geotextile into the pipe openings
material concentrates flow and lowers drain eff-
will be much more efficient. Use of plastic corru-
ciency. Wrapping of the pipe may be useful when
gated, perforated pipe with openings in the de-
finer grained filter materials are best suited be-
pressed portion of the corrugation is an easy way
cause of availability and/or filter grain size re-
of doing this.
quirements. In this case, the geotextile functions
3-5
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