TM 5-811-1/AFJMAN 32-1080
7-5. Direct-Burial Cable Installations.
railroads, cables will be installed in concrete-
encased ducts for protection. Under railroads and
Cables will be installed not less than the mini-
airfield crossings, concrete-encased ducts must be
mum depth required by the NEC or, excluding
steel-reinforced.
Alaska and other permafrost areas, as necessary to
b. Markers. Cable markers will be located near
be below the frost line, whichever is greater.
the ends of cable runs, at each cable joint or splice,
a. Protection. In some locations, nonmetallic-
at approximately every 500 feet along cable runs,
jackets may not provide sufficient cable protection.
and at changes in direction of cable runs. In
Metal armor provides protection from rodents.
addition to markers, a 3-inch wide 5-mil, brightly
Direct-burial cable with concentric neutral, in-
colored plastic tape placed approximately 12
stalled in ducts, will incorporate the same overall
inches below finished grade will be used. Where
jacket as that specified for direct burial. Where
cable is used for lighting circuits and the lighting
buried cable warning is required by the using
poles effectively provide indication of direction
agency, tape manufactured for this purpose will be
changes, markers are not required. Markers will
provided. Where installed under traffic areas or
be similar to the one shown on figure 7-10.
ELEVATION
PLAN
ELEVATION
PLAN
LEVEL CABLE TURN
LEVEL OFFSET CABLE
I
ELEVATION
PLAN
NONLEVEL OFFSET CABLE
US Army Corps of Engineers
Figure 7-4. Factors Influencing Manhole Design.
7-10
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