Mechanical Properties and Strength of Aged Cast Iron Water Pipes

The problem of aging water pipes manifesting leaks and breaks is common to municipalities throughout the North American continent and the world. The age distribution of the failing pipes is broad and the pipe material originates from periods when different manufacturing technologies were employed. Consequently, cast iron pipes exhibit a significant variability of material properties. In addition, these pipes are also in a more or less advanced state of deterioration as a result of corrosion phenomena. A general knowledge of the properties and state of deterioration of a water main network is needed to understand the failure mechanisms contributing to water pipe failure. Among them, knowledge of the mechanical properties of the pipe material itself is fundamental. To achieve this goal, an extensive pipe and soil sampling and testing program was undertaken on excavated pipes in Toronto, Ontario. The mechanical tests performed on pipes included tension, compression, and ring bearing tests as well as full-scale longitudinal bending tests. The outcome of this experimental investigation contributes towards a better understanding of the complex phenomena involved in the pipe failure process.