Page 46 - Buried Pipe Design

24 Chapter Two

Figure 2.7 Load proportioning according to Marston’s theory
for a flexible pipe.
Linear Spring

P
P
K = P/Δ

K
1
Δ
Figure 2.8 Graphic of linear spring.

deflection because of its stiffness. It is even possible to think of soil as
being a nonlinear spring that resists movement or deflection because
of its stiffness (Fig. 2.9).
When we draw an analogy between a rigid pipe represented by a
stiff spring in comparison to soil at its sides, represented by more
flexible springs, and then place a load or weight on this spring sys-
tem representing a rigid pipe in soil, we can easily visualize the
soil deforming and the pipe carrying the majority of the load (see a
in Fig. 2.10). If the situation is reversed and we place a flexible