Structural Mechanics of Buried Pipes

7 Pages·1999·0.264 MB·English

by  Reynold King Watkins, Loren Runar Anderson

STRUCTURAL
MECHANICS
OF
BURIED PIPES
Reynold King Watkins
Utah State University
Logan, Utah
Loren Runar Anderson
Utah State University
Logan, Utah
CRC Press
Boca Raton London New York Washington, D.C.
©2000 CRC Press LLC
©2000 CRC Press LLC
GENERAL NOTATION
Geometry
A = cross sectional wall area per unit length of pipe,
B = breadth of the trench
D = pipe (tank) diameter,
H = height of soil cover,
h = height of water table,
L = length of tank or pipe section,
r = radius of curvature of the pipe (tank) cylinder,
R = radius of a bend in the pipe,
t = thickness of the wall,
x = horizontal coordinate axis,
y = vertical coordinate axis,
z = longitudinal axis (with exceptions),
b = angle of soil shear plane.
Forces, Pressures, and Stresses
P = external pressure on the pipe or tank,
P' = internal pressure,
p = vacuum in the pipe or tank,
Q = concentrated force,
W = surface wheel load,
g = unit weights,
s = direct (normal) stress,
t = shearing stress.
Subscripts refer to directions of forces and stresses.
Properties of Materials
c = cohesion of soil,
E = modulus of elasticity of pipe (tank) material,
S = allowable stress (strength) of material,
g = unit weight of material,
n = Poisson ratio,
j = soil friction angle.
©2000 CRC Press LLC
CONTENTS
Chapter
1 Introduction
2 Preliminary Ring Design
3 Ring Deformations
4 Soil Mechanics
5 Pipe Mechanics
6 Ring Stresses
7 Ring Deflection
8 Ring Stiffness
9 Non-circular Cross Sections
10 Ring Stability
11 Encased Flexible Pipes
12 Rigid Pipes
13 Minimum Soil Cover
14 Longitudinal Mechanics
15 Thrust Restraints
16 Embedment
17 Parallel Pipes and Trenches
18 Special Sections
19 Stress Analysis
20 Plastic Pipes
21 External Hydrostatics
22 Buried Tanks and Silos
23 Flotation
24 Leaks in Buried Pipes and Tanks
25 Long-Span Structures
26 Non-circular Linings and Coatings
27 Risers
28 Analysis of Buried Structures by the Finite Element Method
29 Application of Finite Element Analysis to a Buried Pipe
30 Economics of Buried Pipes and Tanks
Appendix A: Castigliano's Equation
Appendix B: Reconciliation of Formulas for Predicting Ring
Deflection
Appendix C: Similitude
Appendix D: Historical Sketch
Appendix E: Stress Analysis
Appendix F: Strain Energy Analysis
©2000 CRC Press LLC
PREFACE
Buried pipes are an important medium of transportation. Only open channels are less costly to construct.
On the average, pipelines transport over 500 ton-miles of product per gallon of fuel. Gravity systems
require no fuel for pumping. Ships transport 250 ton-miles per gallon. Rails transport 125 ton-miles per
gallon. Trucks transport 10 ton-miles per gallon. Aircraft transport less than 10 ton-miles per gallon of
fuel.
Buried pipelines are less hazardous, and less offensive environmentally than other media of transportation.
They produce less contamination, eliminate evaporation into the atmosphere, and generally reduce loss and
damage to the products that are transported.
The structural mechanics of buried pipes can be complicated -- an interaction of soil and pipe each with
vastly different properties. Imprecisions in properties of the soil embedment are usually so great that
complicated analyses are not justified. This text is a tutorial primer for designers of buried structures --
most of which are pipes. Complicated theories are minimized. Fundamentals of engineering mechanics
and basic scientific principles prevail.
"Science is understanding gained by deliberate inquiry." -- Philip Handler
ACKNOWLEDGMENT
Gratitude is expressed to Becky Hansen for her patient and expert preparation of manuscript.
©2000 CRC Press LLC
©2000 CRC Press LLC