Page 39 - Buried Pipe Design

External Loads 17

H H e

D C

h
H

dh

A B

s m s g
s f d c

pB c

s g

s f
(b)
Figure 2.4 (Continued)

In conjunction with positive projecting conduits, Marston determined
the existence of a horizontal plane above the pipe where the shearing
forces are zero. This plane is called the plane of equal settlement. Above
this plane, the interior and exterior prisms of soil settle equally. The
condition where the plane of equal settlement is real (it is located within
the embankment) is called an incomplete projection or an incomplete
ditch condition. If the plane of equal settlement is imaginary (the shear
forces extend all the way to the top of the embankment), it is called a
complete ditch or complete projection condition.