Page 85 - Buried Pipe Design

External Loads 61

h

P
Figure 2.32 Pressure distribution on a pipe in a liquefied
soil. Buckling at bottom is possible.

fill the jar to the top with water. Replace the lid and shake as before;
remove the lid and turn upside down. The wet sand will stay in the jar
because it has not liquefied.
If the embedment liquefies when a circular pipe is empty, the ring
may be subjected to the hydrostatic pressures shown in Fig. 2.32. If
somehow flotation is prevented, catastrophic collapse may occur from
the bottom according to the classical buckling equation

Pr 3 E t 3
3 or h for plain wall pipe
EI 4 r
Example Problem 2.10 What is the height h of the water table above the
bottom of a steel pipe in embedment so loose that it can liquefy and cause
catastrophic ring collapse?

Pipe: D 105 in
t 0.5

r
105
t
3
Soil: 125 lb/ft saturated
h height of water table above invert
P h

3 30 10 6 3
E
t
Solving yields h (0.00952) 89.6 in 7.46 ft
4
r
4 (125/1728)