Possibilistic approach for consideration of uncertainties to estimate structural capacity of ageing cast iron water mains

Drinking water distribution networks form essential components of all urban centres. Water mains buried in the soil-backfill are exposed to different deleterious reactions, with the result being that the design factor of safety may significantly degrade, leading to structural failure. In particular, metallic distribution and trunk mains are subject to corrosion. Proactive pipeline management, which entails timely maintenance, repair, and renovation, can increase the service life of pipes. Several nondestructive evaluation techniques have recently become available to measure the remaining wall thickness of metallic pipes. In this paper, a previously developed analytical model based on Winkler-type pipe-soil interaction (WPSI) is cast in a possibilistic framework to translate the remaining pipe wall thickness to current structural factor of safety. The WPSI model takes into consideration external (traffic, frost, etc.) and internal (operating and surge pressures) loads, temperature changes, and loss of bedding support and the reduction of pipe structural capacity in the presence of corrosion pits. Uncertainties associated with the input data-parameters are handled using fuzzy arithmetic operations and interpreted through possibility theory. A Monte Carlo type random sampling method is carried out for performing sensitivity analyses to identify the critical data-parameters that merit further investigation.