ABSTRACT
Longitudinal mechanics of buried pipes is the analysis of longitudinal deformations compared to performance limits of deformation. One excessive deformation is fracture for which corresponding strain limits can be identified. If the pipe changes length enough to shear off appurtenances or to allow leakage of couplings, deformation is excessive and corresponding strain limits can be identified. If the strains can be evaluated, then corresponding stresses can be used as alternative bases for design. The principal causes of longitudinal stress (strain) are:
1. Changes in temperature and pressure, which cause relative lengthening or shortening of the pipe with respect to soil and thrust restraints,
2. Axial thrust is the result of internal pressure or vacuum at "thrustors" (valves, caps, reducers, wye's, tee's elbows, etc.),
3. Beam bending, which causes flexural stresses. Typical causes of beam bending are: a) Placement of pipe sections on timbers or mounds or piers for vertical alignment, b) Non-uniform settlement of the bedding, c) Side-hill soil creep or landslide, and massive soil movement or settlement.
