Using sensitivity analysis to identify the critical factors that lower the factor of safety of large-diameter cast iron mains

Abstract

The aim of the paper was to identify the pipe and soil parameters that reduce the factor of safety against failure of large-diameter cast iron (CI) water mains. A mechanics model was developed and used to examine the sensitivity of 29 parameters on pipe factor of safety. The expected value and range of the 29 parameters were based on representative values taken from the research literature. Unsurprisingly, results showed that increasing wall thickness for all pipe diameters increased the factor of safety. Increasing the value of the final pit depth rate, the pitting depth scaling constant, and the corrosion rate inhibition factor lowered the pipe factor of safety. For pipes smaller than 762 mm, increasing diameter produced a higher incremental increase in strength than in loading and increased the factor of safety. Future work should focus on better establishing the relationship between the pipe and soil properties and environmental factors.

Keywords:

• Water distribution
• water mains
• pipe corrosion
• factor of safety
• failure
• loads