Page 151 - Buried Pipe Design

Design of Gravity Flow Pipes 125

The pressure on pipe due to dead load is

P d H 120 1.5 180 lb/ft 2
or
P d D 180(2) 360 lb/ft

For live load on pipe, use Boussinesq equation:
0.477WD 0.477 20,000 2
w l 8480 lb/ft
2
2
H (1.5)
w l 8480 2
P l 4240 lb/ft
D 2
P P d P l 180 4240 4420 lb/ft 2

Total vertical load (per length) on pipe V w d w l 360 8480
8840 lb/ft 737 lb/in. The ring compression stress is

PD V 737 2

t 537 lb/in
2t 2t 2(0.686)
The pipe wall will not crush. It is interesting to note that the total load
2
of 4420 lb/ft is equivalent to a static load of about 37 ft of cover for soil
2
weighing 120 lb/ft . Thus, the soil in the pipe zone should be compacted to
a density required for 37 ft of cover.
For the dead load on section AA, use Eq. (3.26),
r 2
w d (X 2r)(H r)
2

(1 2)(1.5 1) 120
2
712 lb/ft (dead load on section AA)

712 2
or P d 712 lb/ft
w d
X 1
For live load on section AA, the live load w l can be evaluated by Boussinesq
equation, (3.25), where

W
P l 0.477 2 total live load on section AA
H