Estimating time to failure of cast-iron water mains

Water distribution networks form essential components of water supply systems in most urban centres. Water mains buried in the soil/backfill are exposed to different deleterious reactions and—as a result—their design factors of safety may significantly degrade with time, leading to structural failure. In most cases, a combination of circumstances leads to the failure of a pipe. Factors contributing to pipe failure include: operational conditions; design parameters; external loads (traffic, frost, etc.); internal loads (operating and surge pressures); temperature changes; loss of bedding support, pipe properties and condition; and corrosion pit geometry. These are recorded rarely, if at all, and it is therefore very difficult to ascertain the precise causes of failure. Even if all this information were available, any attempt to estimate the pipe condition state would involve considerable uncertainty owing to large spatial and temporal variability that is inherent in this information. Estimation of time to ...