Page 285 - Buried Pipe Design

256 Chapter Five

Case I:

490 400
P p

w W 5200 490 2228 lb/ft
P
Since 2228 2136, class 100 is acceptable.

Case II:

490 250

w 5200 490 3639 lb/ft 2780 lb/ft

Class 100 is acceptable.
Figure 14E of AWWA C401 (see Fig. 5.3) is a solution to r sd p 0.70,
K 0.192, and 120 lb/ft . Class 100 pipe would therefore perform
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for any conditions which are below the lowest design curve. The class
designations are based on case I with a class C bedding, excavated cou-
pling holes, and 5.0 ft of cover.

Example 5.3—Transmission pipe design A 24-in-diameter transmission line
will deliver water at 7000 gal/m and 5.0 ft/s from a reservoir to a treatment
plant 10 mi away. The pipe will be buried 5.0 ft deep in a 4.0-ft-wide trench
in sand carefully compacted or bedded with a coarse, granular material up
to the spring line. Surge devices and valve operating equipment will keep
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surge pressures to a maximum of 50 lb/in . The system will operate at a
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maximum pressure of 150 lb/in . Determine the appropriate asbestos-
cement transmission pipe. (See AWWA C402.)
1. Determine the earth load.

H 5.0
1.25 (from Fig. 2.2, C d 1.1)
B d 4.0

K 0.165 sand

2
W d 1.1 (120) (4.0) 2112 lb/ft
The load at the transition width is

H 5.0
2.27 (from Fig. 2.6, B d /B c 1.8)
B c 26.4/12
r sd p 0.5