Development of a Fuzzy Risk Ranking Model for Prioritizing Manhole Inspection

Abstract

Manholes are designed to provide access points to underground sewer networks for inspection and maintenance. Manhole collapses, although rare, can result in severe consequences and have a significant effect on the performance of the sewer. This paper presents a case study on the development of a risk ranking model using fuzzy set theory and the analytical hierarchy process for individual manholes of sewer networks. The fuzzy risk ranking model (FRM) considered both the likelihood and consequence of collapse. The performance of the FRM was validated against 10 manholes with known poor condition. The results were also compared against a previously developed risk ranking scheme, with regards to consistency and repeatability of the relative ranking of assets. The results suggested that the FRM may provide better performance, although only limited data were available for validation. The process adopted in constructing the scheme is considered to be systematic and auditable.