TM 5820-4/AFM 885, Chap 4
Notes:
1. Corrugated steel pipe will conform to there requirements of Federal Specification WW-P-4O5.
2. The suggested maximum heights of cover shown in the table are calculated on the basis of the current AASHTO
Standard Specifications for Highway Bridges and are based on circular pipe.
3. Soil conditions, trench width and bedding conditions vary widely throughout varying climatic and geographical areas.
4. Calculations to determine maximum cover should be made for all individual pipe and culvert installations underlying
roads, streets and open storage areas subject to H20 live loads. Cooper E80 railway loadings should be independently
made.
5. Cover depths are measured from the bottom of the subbase of pavements, or the top of unsurfaced areas, to top of pipe.
6. Calculations to determine maximum cover for Cooper E80 railway loadings are measured from the bottom of the tie
to the top of the pipe.
7. If pipe produced by a manufacturer exceeds the strength requirements established by indicated standards then cover
depths may be adjusted accordingly.
8. See table C-9 for suggested minimum cover requirements.
tion, use of granular material, use of concrete, and
unusual installation conditions, a detailed analy-
similar special requirements. Although such re-
sis will be made so that ample safeguards for the
finement is not considered necessary, at least for
pipe will be provided with regard to strength and
standardized cover requirements, select, fine
resistance to deflection due to loads. Determina-
granular material can be used as an aid in shaping
tions for deflections of flexible pipe should be made
the bedding, particularly where foundation con-
if necessary. For heavy live loads and heavy loads
ditions are difficult. Also, where economically
due to considerable depth of cover, it is desirable
available, granular materials can be used to good
that a selected material, preferably bank-run
advantage for backfill adjacent to the pipe. When
gravel or crushed stone where economically avail-
culverts or storm drains are to be installed in un-
able, be used for backfill adjacent to the pipe. Table
stable or yielding soils, under great heights of fill,
C-9 suggests guidelines for minimum cover to pro-
tect the pipe during construction and the mini-
or where pipe will be subjected to very heavy live
loads, a method of bedding can be used in which
mum finished height of cover.
the pipe is set in plain or reinforced concrete of
C-1O. Bedding of pipe (culverts and storm
suitable thickness extending upward on each side
of the pipe. In some instances, the pipe may be
drains). The contact between a pipe and the foun-
totally encased in concrete or concrete may be
dation on which it rests is the pipe bedding. It has
placed along the side and over the top of the pipe
an important influence on the supporting strength
(top or arch encasement) after proper bedding and
of the pipe. For drainpipes at military installa-
partial backfilling. Pipe manufacturers will be
tions, the method of bedding shown in figure C-3
helpful in recommending type and specific re-
is generally satisfactory for both trench and pos-
quirements for encased, partially encased, or spe-
itive projecting (embankment) installations. Some
cially reinforced pipe in connection with design
designs standardize and classify various types of
for complex conditions.
bedding in regard to the shaping of the founda-
C-5
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