City Research Online

Abstract

A brief history of water distribution mains and the materials used is given together with a review of research into the fracture of water mains. Although much was known about the fracture of pipes there has not been a systematic study of failures to investigate the primary causes.

An analysis of mains fracture data shows that for small and medium size pipes, there are two primary fracture triggering mechanisms, corrosion and longitudinal bending, and a variety of secondary mechanisms. A flow chart linking the primary and secondary fracture triggering mechanisms with the type of fracture they produce is given.

The effect of longitudinal bending is analysed first by using an elastic model to obtain design formulae, by which the performance of various materials and pipe sizes can be compared. The formulae are also used to investigate the vulnerability of spun and ductile iron to the onset of fissure corrosion. The effect of a concentrated surface load is also investigated and found to be a secondary effect for small and medium size mains.

A second mathematical model is described in which the ground can have a non-linear pressure-displacement relationship and the pipeline material a non-linear stress-strain relationship. The model was used to investigate the effect of differential displacement on pipelines in non-homogeneous soils and from the results obtained recommendations are made with regard to pipe laying procedures.

Experimental investigations into the effect of differential displacement on a buried pipeline are described and the results compared with those obtained from the second mathematical model.

Finally as the major causes of fractures are known, the economics of mains replacement are discussed with regard to finding a fracture regression curve or base fracture rate with which to formulate a replacement policy.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General) T Technology > TC Hydraulic engineering. Ocean engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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