Effects of operational loads on buried water pipes using field tests

Abstract

Water pipelines are vital assets which are a critical part of a nation’s infrastructure due to their importance for the supply of mankind’s basic need: water. The safety of these transmission pipelines is critical to a nation’s socioeconomic development. Since most in-service pipelines were buried in the last century, the safety of these lifelines is of concern because they are buried and most importantly, they are approaching the end of their intended service lives. Failure predictive models are often benchmarked against analytical tools and/or laboratory test data due to the unrealistic nature of field test verification. The study reported here investigates the performance monitoring of field-buried pipes using comprehensive field instrumentation of a 660 mm diameter cast iron pipe in the water network of Sydney, NSW. A number of field tests were conducted to evaluate the buried pipe’s response to various controlled loading scenarios, such as multiple traffic loads, different speeds, braking scenarios, pavement surface conditions and internal water pressure loading/unloading magnitudes. The results showed different pipe strains under varying traffic loads and speeds with a 20–30% strain reduction under moving traffic compared to stationary traffic. The results also revealed that the pipe strains encountered under internal water pressures are significantly larger (∼7-fold) than the strains under traffic loads, although the pipe deformation under both operational loads is considerably lower than the failure strains of the pipe. Full-scale 3-D FE analyses were conducted to demonstrate the use of field data for the verification of numerical models which are typically used to predict the responses of buried pipes subjected to operational loads. The outcomes of the study will serve as valuable information to supplement the failure prediction and maintenance evaluation of buried water pipes which are fast approaching the end of their service lives.