Effects of Corrosion Pits on Wall Stresses in Cast-Iron Water Mains
Publication: Journal of Pipeline Systems Engineering and Practice
Volume 8, Issue 4
Abstract
Circumferential cracking or ring fracture has been identified as the most common type of failure mode for cast-iron water mains. However, the cause of circumferential cracking in water mains is not well understood. A number of different postulates exist in the literature on the causes of longitudinal stresses leading to circumferential cracking. The postulates are, however, not proven. This paper presents a finite element analysis to investigate the effect of corrosion pits on the failure mechanism of cast-iron water mains. The study shows that corrosion pits, voids in the bedding, and high relative stiffness of the pipe (with respect to the surrounding soil) can contribute to longitudinal stress development in the pipe wall. Longitudinal stress is generally higher than circumferential stress for a pipe with high relative stiffness. For a particular pipe, longitudinal stress is higher for smaller corrosion pits. Localized forces on the pipe wall from the surrounding ground can increase the longitudinal stress significantly. A localized support equivalent to a spring with a spring constant of can result in circumferential cracking of pipes. Based on the findings, a failure hypothesis has been provided for cast-iron water mains.
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Acknowledgments
The financial support for this research was provided by Research and Development Corporation of Newfoundland and Labrador, which is gratefully acknowledged. The authors would also like to acknowledge the comments from Dr. Bipul Hawlader in the Department of Civil Engineering at Memorial University of Newfoundland.
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Information & Authors
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Published In
Journal of Pipeline Systems Engineering and Practice
Volume 8 • Issue 4 • November 2017
Copyright
© 2017 American Society of Civil Engineers.
History
Received: Nov 30, 2016
Accepted: May 8, 2017
Published online: Aug 11, 2017
Published in print: Nov 1, 2017
Discussion open until: Jan 11, 2018
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