Flexible pipes are pipes that can deflect at least 2% of the pipe diameter without any damage. When compared with rigid pipes such as precast concrete pipes, flexible pipes are comparatively weak and they count predominantly on the composite action between pipe deflection and backfilled soils to achieve structural stability. On the other hand, rigid pipes rely mainly on their inherent structural strength to carry imposed earth and traffic loads. Hence, improper installation of flexible pipes would compromise structural performance and results in risk failure.
The design of flexible pipes is complex as the soil boundary conditions include not only the backfilling trench but also the envelope of original soils outside the trench. It requires detailed assessment of theoretical pipe deflection, long-term bending strain and buckling pressure.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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