Page 316 - Buried Pipe Design

Steel and Ductile Iron Flexible Pipe Products 287

y
P v

Original Pipe
(No Load)
Deformed Pipe D
(Vertical Soil
Pressure P )
v

x D x
Figure 6.1 Ring deflection of buried flexible pipe.

stress f is specified, then the computed compressive stress S is deter-
c
mined by the formula S P (D/2A). (See Fig. 6.2.)
v
The vertical soil pressure P is usually defined as the soil pressure
v
at the level of the top of the pipe if no pipe were in place. This implies
that the ring cross section compresses precisely as much as the soil.
Actually the pipe in place may cause pressure concentration or pres-
sure relief (if the soil is more or less compressible than the ring cross
section) which could possibly be taken into account by a stress concen-
tration factor.

A
c

P D/2 P D/2
V
V
D

Figure 6.2 Ring compression of buried flexible pipe. A area of wall cross-section per
unit length of pipe area/l; I moment of inertia about neutral axis per unit length of
pipe; E modulus of elasticity of pipe material; c distance to most remote fiber from
neutral axis; l unit length of pipe.