Moser A.P., Folkman S. Buried Pipe Design
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5 0.29 250 0.26 250 0.23 250 0.20 250
6 0.29 250 0.26 250 0.23 250 0.20 250
7 0.30 250 0.27 250 0.23 250 0.21 250
8 0.30 250 0.27 250 0.24 250 0.21 250
9 0.31 250 0.28 250 0.24 250 0.21 250
10 0.32 250 0.29 250 0.24 250 0.21 250
12 0.35 300 0.31 250 0.25 250 0.22 250
14 0.37 350 0.33 250 0.26 250 0.22 250
16 — — 0.35 300 0.28 250 0.23 250
20 — — — — 0.32 250 0.24 250
24 — — — — 0.35 300 0.28 250
28 — — — — 0.38 350 0.32 250
32 — — — — — — 0.35 300
24 2.50
‡‡
0.36 250 0.32 200 0.26 200 0.22 200
3 0.33 200 0.30 200 0.25 200 0.22 200
4 0.32 200 0.29 200 0.25 200 0.21 200
5 0.31 200 0.28 200 0.24 200 0.21 200
6 0.31 200 0.28 200 0.24 200 0.21 200
7 0.32 200 0.29 200 0.25 200 0.22 200
8 0.33 200 0.30 200 0.25 200 0.22 200
9 0.35 250 0.30 200 0.26 200 0.22 200
10 0.36 250 0.31 200 0.26 200 0.22 200
12 0.39 300 0.33 200 0.27 200 0.23 200
14 0.41 350 0.36 250 0.29 200 0.24 200
16 — — 0.38 300 0.31 200 0.24 200
20 — — — — 0.36 250 0.26 200
24 — — — — 0.40 300 0.32 200
28 — — — — 0.43 350 0.37 250
32 — — — — — — 0.40 300
30 2.50
‡‡
0.40 250 0.34 150 0.29 150 0.24 150
3 0.37 200 0.33 150 0.28 150 0.23 150
4 0.36 200 0.32 150 0.27 150 0.23 150
5 0.35 200 0.31 150 0.26 150 0.23 150
6 0.35 200 0.31 150 0.27 150 0.23 150
349
7 0.36 200 0.32 150 0.27 150 0.23 150
8 0.37 200 0.33 150 0.27 150 0.23 150
9 0.39 250 0.34 150 0.28 150 0.24 150
10 0.41 250 0.35 200 0.29 150 0.24 150
12 0.44 300 0.38 200 0.30 150 0.25 150
14 0.48 350 0.41 250 0.33 150 0.26 150
16 — — 0.44 300 0.37 200 0.26 150
20 — — — — 0.43 300 0.29 150
24 — — 0.48 350 0.38 200
28 — — — — 0.44 300
32 — 0.48 350
36 2.50
‡‡
0.43 250 0.37 150 0.31 150 0.25 150
3 0.41 200 0.36 150 0.30 150 0.25 150
4 0.39 200 0.34 150 0.29 150 0.24 150
5 0.39 200 0.34 150 0.29 150 0.24 150
6 0.39 200 0.34 150 0.29 150 0.24 150
7 0.40 200 0.35 150 0.29 150 0.24 150
8 0.42 200 0.36 150 0.30 150 0.25 150
9 0.44 250 0.38 150 0.31 150 0.25 150
10 0.46 250 0.39 200 0.31 150 0.26 150
12 0.50 300 0.42 200 0.33 150 0.27 150
14 0.54 350 0.46 250 0.38 150 0.28 150
16 — — 0.50 300 0.43 250 0.29 150
20 — — — — 0.51 300 0.33 150
24 — — — — 0.56 350 0.44 250
TABLE 6.14 Thickness for Earth Load plus Truck Load (Continued )
Laying condition
Type 1 Type 2 Type 3 Type 4 Type 5
Total Total Total Total Total
Depth of calculated Use calculated Use calculated Use calculated Use calculated Use
Size, cover,
*
thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure
inft in class in class in class in class in class
350
28 — — — — — — 0.51 300
32 — — — — — — 0.56 350
42 2.50
‡‡
0.47 200 0.40 150 0.32 150 0.27 150
3 0.44 200 0.38 150 0.31 150 0.26 150
4 0.42 200 0.37 150 0.30 150 0.25 150
5 0.43 200 0.37 150 0.31 150 0.26 150
6 0.43 200 0.37 150 0.31 150 0.26 150
7 0.44 200 0.38 150 0.31 150 0.26 150
8 0.46 200 0.40 150 0.32 150 0.26 150
9 0.48 250 0.41 150 0.33 150 0.27 150
10 0.50 250 0.43 200 0.34 150 0.27 150
12 0.55 300 0.47 200 0.36 150 0.28 150
14 0.60 350 0.52 250 0.43 200 0.30 150
16 — — 0.57 300 0.49 250 0.31 150
20 — — — — 0.57 300 0.38 150
24 — — — — — — 0.50 250
28 — — — — 0.58 350
32 — — — — — 0.63 350
48 2.50
‡‡
0.50 200 0.44 150 0.35 150 0.29 150
3 0.48 200 0.42 150 0.34 150 0.28 150
4 0.46 150 0.41 150 0.33 150 0.28 150
5 0.47 200 0.41 150 0.34 150 0.28 150
6 0.48 200 0.41 150 0.34 150 0.28 150
7 0.49 200 0.43 150 0.35 150 0.28 150
8 0.51 200 0.44 150 0.35 150 0.29 150
9 0.54 250 0.46 150 0.37 150 0.29 150
10 0.56 250 0.48 200 0.38 150 0.30 150
12 0.62 300 0.54 250 0.40 150 0.31 150
14 0.67 350 0.60 300 0.49 200 0.33 150
16 — — 0.65 350 0.56 250 0.34 150
20 — — — — 0.66 350 0.43 150
24 — — — — 0.57 250
28 — — — — — — 0.66 350
351
54 2.50
‡‡
0.54 200 0.47 150 0.38 150 0.31 150
3 0.53 200 0.46 150 0.37 150 0.30 150
4 0.51 150 0.44 150 0.36 150 0.30 150
5 0.52 200 0.45 150 0.37 150 0.30 150
6 0.53 200 0.46 150 0.37 150 0.30 150
7 0.54 200 0.47 150 0.38 150 0.31 150
8 0.57 200 0.49 150 0.39 150 0.32 150
9 0.60 250 0.51 150 0.40 150 0.32 150
10 0.63 250 0.53 200 0.41 150 0.33 150
12 0.69 300 0.61 250 0.44 150 0.34 150
14 0.75 350 0.68 300 0.55 200 0.36 150
16 — — 0.73 350 0.63 250 0.37 150
20 — — — — 0.74 350 0.48 150
24 — — — — 0.64 250
28 — — — 0.74 350
60 2.50
‡‡
0.56 200 0.48 150 0.39 150 0.32 150
3 0.54 150 0.47 150 0.38 150 0.31 150
4 0.53 150 0.46 150 0.38 150 0.31 150
5 0.54 150 0.47 150 0.38 150 0.31 150
6 0.55 200 0.48 150 0.39 150 0.31 150
7 0.57 200 0.49 150 0.39 150 0.32 150
8 0.59 200 0.51 150 0.40 150 0.33 150
9 0.63 250 0.53 150 0.42 150 0.33 150
10 0.67 250 0.55 200 0.43 150 0.34 150
12 0.74 300 0.65 250 0.46 150 0.35 150
TABLE 6.14 Thickness for Earth Load plus Truck Load (Continued )
Laying condition
Type 1 Type 2 Type 3 Type 4 Type 5
Total Total Total Total Total
Depth of calculated Use calculated Use calculated Use calculated Use calculated Use
Size, cover,
*
thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure thickness,
†
pressure
inft in class in class in class in class in class
352
14 0.79 350 0.72 300 0.58 200 0.37 150
16 — — 0.78 350 0.67 250 0.38 150
20 — — — — 0.79 350 0.51 150
24 — — — — 0.68 250
28 — — — — — — 0.79 350
64 2.50
‡‡
0.58 200 0.50 150 0.40 150 0.32 150
3 0.56 150 0.49 150 0.39 150 0.32 150
4 0.55 150 0.48 150 0.39 150 0.32 150
5 0.56 150 0.48 150 0.39 150 0.32 150
6 0.57 200 0.49 150 0.40 150 0.32 150
7 0.59 200 0.51 150 0.41 150 0.33 150
8 0.62 200 0.53 150 0.42 150 0.33 150
9 0.67 250 0.55 150 0.43 150 0.34 150
10 0.70 250 0.58 200 0.45 150 0.35 150
12 0.78 300 0.68 250 0.48 150 0.37 150
14 0.84 350 0.76 300 0.61 200 0.38 150
16 — — 0.82 350 0.70 250 0.40 150
20 — — — — 0.83 350 0.54 150
24 — — — — 0.72 250
28 — — — 0.83 350
NOTE: To convert inches (in) to millimeters (mm), multiply by 25.4; to convert feet (ft) to meters (m), multiply by 0.3048.
*
Pipe may be available for depths of cover greater than those shown in the table.
†
Total calculated thickness includes service allowance and casting tolerance added to net thickness.
‡
For pipe 14 in (356 mm) and larger, consideration should be given to laying conditions other than type 1.
SOURCE: Table 12 from AWWA C150.
353
TABLE 6.15 Thickness for Internal Pressure
Rated water working pressure, lb/in
2
150 200 250 300 350
Total Total Total Total Total
Pipe calculated Use calculated Use calculated Use calculated Use calculated Use
size, thickness,
*
pressure thickness,
*
pressure thickness,
*
pressure thickness,
*
pressure thickness,
*
pressure
in in class in class in class in class in class
3 0.15 350 0.16 350 0.16 350 0.17 350 0.17 350
4 0.16 350 0.16 350 0.17 350 0.18 350 0.18 350
6 0.17 350 0.18 350 0.19 350 0.20 350 0.20 350
8 0.18 350 0.19 350 0.21 350 0.22 350 0.23 350
10 0.21 350 0.22 350 0.23 350 0.25 350 0.26 350
12 0.22 350 0.23 350 0.25 350 0.27 350 0.28 350
14 0.24 250 0.26 250 0.28 250 0.30 300 0.31 350
16 0.25 250 0.27 250 0.30 250 0.32 300 0.34 350
18 0.27 250 0.29 250 0.31 250 0.34 300 0.36 350
20 0.28 250 0.30 250 0.33 250 0.36 300 0.38 350
24 0.30 200 0.33 200 0.37 250 0.40 300 0.43 350
30 0.34 150 0.38 200 0.42 250 0.45 300 0.49 350
36 0.38 150 0.42 200 0.47 250 0.51 300 0.56 350
42 0.41 150 0.47 200 0.52 250 0.57 300 0.63 350
48 0.46 150 0.52 200 0.58 250 0.64 300 0.70 350
54 0.51 150 0.58 200 0.65 250 0.72 300 0.79 350
60 0.54 150 0.61 200 0.68 250 0.76 300 0.83 350
64 0.56 150 0.64 200 0.72 250 0.80 300 0.87 350
NOTES:
1. To convert inches (in) to millimeters (mm), multiply by 25.4; to convert pounds per square inch
(lb/in
2
) to kilopascals (kPa), multiply by 6.895.
2. The thicknesses shown are adequate for the rated working pressure plus a surge allowance of 100
psi (689 kPa). Calculations are based on a minimum yield strength in tension of 42,000 psi (289,590 kPa)
and a 2.0 safety factor times the sum of working pressure and 100 psi (689 kPa) surge allowance.
*
Total calculated thickness includes service allowance and casting tolerance added to net thickness.
SOURCE: Table 13 from AWWA C150.
354
Steel and Ductile Iron Flexible Pipe Products 355
3 350 0.25 78 88 99 100
‡
100
‡
4 350 0.25 53 61 69 85 100
‡
6 350 0.25 26 31 37 47 65
8 350 0.25 16 20 25 34 50
10 350 0.26 11
§
15 19 28 45
12 350 0.28 10
§
15 19 28 44
14 250 0.28 ¶ 11
§
15 23 36
300 0.30 ¶ 13 17 26 42
350 0.31 ¶ 14 19 27 44
16 250 0.30 ¶ 11
§
15 24 34
300 0.32 ¶ 13 17 26 39
350 0.34 ¶ 15 20 28 44
18 250 0.31 ¶ 10
§
14 22 31
300 0.34 ¶ 13 17 26 36
350 0.36 ¶ 15 19 28 41
20 250 0.33 ¶ 10 14 22 30
300 0.36 ¶ 13 17 26 35
350 0.38 ¶ 15 19 28 38
24 200 0.33 ¶ 8
§
12 17 25
250 0.37 ¶ 11 15 20 29
300 0.40 ¶ 13 17 24 32
350 0.43 ¶ 15 19 28 37
30 150 0.34 ¶ — 9 14 22
200 0.38 ¶ 8
§
12 16 24
250 0.42 ¶ 11 15 19 27
300 0.45 ¶ 12 16 21 29
350 0.49 ¶ 15 19 25 33
36 150 0.38 ¶ — 9 14 21
200 0.42 ¶ 8
§
12 15 23
250 0.47 ¶ 10 14 18 25
300 0.51 ¶ 12 16 20 28
350 0.56 ¶ 15 19 24 32
42 150 0.41 ¶ — 9 13 20
200 0.47 ¶ 8 12 15 22
250 0.52 ¶ 10 14 17 25
300 0.57 ¶ 12 16 20 27
350 0.63 ¶ 15 19 23 32
48 150 0.46 ¶ — 9 13 20
200 0.52 ¶ 8 11 15 22
250 0.58 ¶ 10 13 17 24
300 0.64 ¶ 12 15 19 27
350 0.70 ¶ 15 18 22 30
54 150 0.51 ¶ — 9 13 20
200 0.58 ¶ 8 11 14 22
250 0.65 ¶ 10 13 16 24
300 0.72 ¶ 13 15 19 27
350 0.79 ¶ 15 18 22 30
NOTE: See p. 356 for footnotes.
TABLE 6.16 Rated Working Pressure and Maximum Depth of Cover
Laying condition
Type 1 Type 2 Type 3 Type 4 Type 5
trench trench trench trench trench
Nominal
Size, Pressure thickness,
in class,
*
lb/in
2
in Maximum depth of cover, ft
†
TABLE 6.16 Rated Working Pressure and Maximum Depth of Cover (Continued )
Laying condition
Type 1 Type 2 Type 3 Type 4 Type 5
trench trench trench trench trench
Nominal
Size, Pressure thickness,
in class,
*
lb/in
2
in Maximum depth of cover, ft
†
60 150 0.54 ¶ 5
§
91320
200 0.61 ¶ 8 11 14 22
250 0.68 ¶ 10 13 16 24
300 0.76 ¶ 13 15 19 26
350 0.83 ¶ 15 18 22 30
64 150 0.56 ¶ 5
§
91320
200 0.64 ¶ 8 11 14 21
250 0.72 ¶ 10 13 16 24
300 0.80 ¶ 12 15 19 26
350 0.87 ¶ 15 17 21 29
NOTE: To convert inches (in) to millimeters (mm), multiply by 25.4; to convert feet (ft) to
meters (m), multiply by 0.3048; and to convert pounds per square inch (lb/in
2
) to kilopascals
(kPa), multiply by 6.895.
*
Ductile iron pipe is adequate for the rated working pressure indicated for each nominal size
plus a surge allowance of 100 lb/in
2
(689 kPa). Calculations are based on a 2.0 safety factor
times the sum of working pressure and 100 lb/in
2
(689 kPa) surge allowance. Ductile iron pipe
for working pressures higher than 350 lb/in
2
(2413 kPa) is available.
†
An allowance for a single H-20 truck with 1.5 impact factor is included for all depths of cover.
‡
Calculated maximum depth of cover exceeds 100 ft (30.5 m).
§
Minimum allowable depth of cover is 3 ft (0.9 m).
¶
For pipe 14 in (356 mm) and larger, consideration should be given to the use of laying con-
ditions other than type 1.
SOURCE: Table 14 from AWWA C150.
TABLE 6.17 Special Thickness Classes of Ductile Iron Pipe
Outside
Thickness class
*
Size, diameter,
50 51 52 53 54 55 56
in inThickness, in
3 3.96 — 0.25 0.28 0.31 0.34 0.37 0.40
4 4.80 — 0.26 0.29 0.32 0.35 0.38 0.41
6 6.90 0.25 0.28 0.31 0.34 0.37 0.40 0.43
8 9.05 0.27 0.30 0.33 0.36 0.39 0.42 0.45
10 11.10 0.29 0.32 0.35 0.38 0.41 0.44 0.47
12 13.20 0.31 0.34 0.37 0.40 0.43 0.46 0.49
14 15.30 0.33 0.36 0.39 0.42 0.45 0.48 0.51
16 17.40 0.34 0.37 0.40 0.43 0.46 0.49 0.52
18 19.50 0.35 0.38 0.41 0.44 0.47 0.50 0.53
20 21.60 0.36 0.39 0.42 0.45 0.48 0.51 0.54
24 25.80 0.38 0.41 0.44 0.47 0.50 0.53 0.56
30 32.00 0.39 0.43 0.47 0.51 0.55 0.59 0.63
36 38.30 0.43 0.48 0.53 0.58 0.63 0.68 0.73
42 44.50 0.47 0.53 0.59 0.65 0.71 0.77 0.83
48 50.80 0.51 0.58 0.65 0.72 0.79 0.86 0.93
54 57.56 0.57 0.65 0.73 0.81 0.89 0.97 1.05
NOTE: To convert inches (in) to millimeters (mm), multiply by 25.4.
*
These special thickness classes were designated standard thickness classes in the 1986
edition of this standard.
SOURCE: Table 15 from AWWA C150.
356
Steel and Ductile Iron Flexible Pipe Products 357
3. The PD/(2A) or ring compression stress where P apparent verti-
cal soil pressure on the pipe (unit weight of soil times height plus
the effect of surface loads at the level of the top of the ring), D
diameter, and A cross-sectional area of the pipe wall per unit
length of pipe.
4. Ring deflection y/D, where y vertical decrease in pipe diameter
and D diameter.
5. Performance limit.
Figure 6.47 Reynold Watkins at the USU test cell.
358 Chapter Six
From the testing program it was concluded that the following three
performance limits are pertinent for ductile iron pipe.
1. Spalling or unbonding of the cement lining—observable by eye
2. Cracking of the ductile iron in the bell—observable by eye
3. Loss of compression in the gasket in the joint—measurable by gage
Of the three, spalling or unbonding of the cement-mortar lining is
the first performance limit to occur as a result of external soil pres-
sure. The second performance limit is bell cracking, and the third,
which seems to be most remote, is loss of compression in the gasket. It
is noteworthy that the two most pertinent parameters in all three per-
formance limits are the ring deflection y/D and the D/t ratio.
Conse-
quently, the same general rationale applies to all three performance
limits. Any one of these three performance limits can be predicted in
terms of y/D and D/t. All three performance limits are discussed in
the following paragraphs. However, only the cracking and spalling of
the lining are considered in detail.
Because of academic emphasis on the stress theory of failure, there
has been great interest in the maximum stress in the ring. Maximum
stress can be calculated by adding the ring compression stress
c
to the flexural stress
f
⌭
However, for ductile iron pipe, flexural stress is not an adequate indi-
cator of performance and need not be used in the design of the ring to
resist external loads. Due to soil-structure interaction, i. e., the lateral
support of soil at the sides in combination with the arching action of
the soil over the pipe, failure does not occur even though the yield
point may have been reached in the outer fibers of the pipe wall. The
first observable sign of distress is cracking of the cement mortar which
is followed by spalling of the cement mortar lining. The performance
limit is not due to stress in the wall, but rather is due to deformation.
Performance limit 1—spalling or unbonding of cement lining. The cause
of cracking and spalling of cement linings in ductile iron pipes is
determined by wall strain—not just ring deflection. In the design of
cement-lined pipe, an arbitrary value of y/D 2 percent maximum is
often specified in order to prevent damage to the cement lining.
t(3y/D)
D (1 2y/D)
PD
2A