Page 110 - Buried Pipe Design

86 Chapter Three

W

r

ΔX ΔX
2 2

Figure 3.6 Basis of Spangler’s derivation of the Iowa formula for deflec-
4
3
tion of buried pipes. X D L KW c r /(EI 0.061er ) (the Iowa formula),
where e 2h/ X, 2r D pipe diameter, K bedding constant, D L
deflection lag factor, and EI stiffness factor (related to pipe stiffness).
(Reprinted, by permission, of Utah State University.)
Equation (3.4) can be used to predict deflections of buried pipe if the
three empirical constants K, D L , and e are known. The bedding constant
K accommodates the response of the buried flexible pipe to the opposite
and equal reaction to the load force derived from the bedding under the
pipe. The bedding constant varies with the width and angle of the bed-
ding achieved in the installation. The bedding angle is shown in Fig. 3.7.

Figure 3.7 Bedding angle.