TM 5820-4/AFM 88-5, Chap 4
increased compaction requirements, and revised
were made during the period 1966 to 1972. The
minimum cover tables.
facilities observed varied from one to more than
30 years of age. The study revealed that buried
e. The necessary minimum cover in certain in-
conduits and associated storm drainage facilities
stances may determine pipe grades. A safe mini-
installed from the early 1940's until the mid-1960's
mum cover design requires consideration of a
appeared to be in good to excellent structural con-
number of factors including selection of conduit
dition. However, many reported failures of buried
material, construction conditions and specifica-
conduits occurred during construction. Therefore,
tions, selection of pavement design, selection of
it should be noted that minimum conduit cover
backfill material and compaction, and the method
requirements are not always adequate during
of bedding underground conduits. Emphasis on
construction. When construction equipment, which
these factors must be carried from the design stage
may be heavier than live loads for which the con-
through the development of final plans and spec-
duit has been designed, is operated over or near
ifications.
an already inplace underground conduit, it is the
f. Tables C-1 through C-6 identify certain sug-
responsibility of the contractor to provide any ad-
gested cover requirements for storm drains and
ditional cover during construction to avoid dam-
culverts which should be considered as guidelines
age to the conduit. Major improvements in the
only. Cover requirements have been formulated
design and construction of buried conduits in the
for asbestos-cement pipe, reinforced and non-rein-
two decades mentioned include, among other items,
forced concrete pipe, corrugated-aluminum-alloy
increased strength of buried pipes and conduits,
Table C1. Suggested Maximum Cover Requirements for Asbestos-Cement Pipe
H20 Highway Loading
Suggested Maximum Cover Above Top of Pipe, ft
Diameter
Circular Section
in.
Class
2000
2500
9000
3750
1500
24
13
16
19
12
9
13
17
24
10
19
15
13
17
18
10
20
25
20
13
17
25
10
21
10
14
17
20
25
24
14
17
10
20
25
27
14
17
11
21
24
30
14
17
26
11
21
33
11
14
17
21
26
36
14
17
42
11
21
26
U.S. Army Corps of Engineers
Notes:
1. The suggested values shown are for average conditions and are to be considered as guidelines only for dead load plus
H20 live load.
2. Soil conditions. trench width and bedding conditions vary widelv throughout varying climatic and geographical areas.
3. Calculations to determine maximum cover should be made for all individual pipe and culvert installations underlying
roads, streets and open storage areas subject to H-20 live loads. Cooper E80 ; railway loadings should be independently
made.
4. Cover depths are measured from the bottom of the subbase of pavements, or the top of unsurfaced areas, to top of pipe.
5. Calculations to determine maximum cover for Cooper E80 railway loadings are measured from the bottom of the tie
to the top of the pipe.
6. The number in the class designation for asbestos-cement pipe is the minimum 3-edge test load to produce failure in
pounds per linear foot. It is independent of pipe diameter. An equivalent to the D-load can be obtained by dividing the
number in the class designation by the internal pipe diameter in feet.
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 C9 for suggested minimum cover requirements.
C-2
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