Lifetime Reliability Assessment of Buried Pipelines Subjected to Corrosion

Cast iron materials were vastly used to fabricate the buried pipelines for water distribution prior to the 1970s in Australia and overseas. Nowadays, there is still a significant amount of ageing cast iron pipes being in service in many water utilities. Cast iron is a brittle material and when large diameter cast iron pipes (diameters above 300mm) further deteriorate, the consequences of failure can be substantial. Focusing on the likelihood of lifetime failure, this study examines the performance of large-diameter cast iron pipes using probabilistic analysis, incorporating uncertainties of governing variables. Finite element analysis has been carried out to study the physical mechanism of buried pipes subjected to complex environmental conditions. The deterioration of cast iron pipes due to corrosion is taken into account. The uncertainties of governing variables, such as the physical properties of soil, cast iron, water pressure and corrosion patterns, in pipe failure risk assessment are considered. Using probabilistic physical modelling, the lifetime probability of failure has been derived and a time-dependent sensitivity analysis will be presented. The results of this probabilistic physical modelling are compared with cohorts of failure data from two Australian water utilities to examine the underlying trends from both physical modelling and statistical analysis.