Damages in vitrified clay sewers in service for 130–142 years

Abstract

The aim of the study was to analyze the damage occurring in vitrified clay sewers operated for a period of 130–142 years based on the results of their CCTV testing. In view of the fact that there are very large differences in the assessment of the forecast lifetime of sewer pipes, as reported by the different institutions, and significant differences in the survival functions developed for these pipes, particular attention has been paid to identification of the causes of this situation. One of the most important results of the research and analyses conducted is demonstration that models predicting the durability of vitrified clay pipes and the survival functions created for them should be developed separately for sewers laid in dry soils and water-saturated soils. The research has also shown that various so-called primary damages were observed in sewers, which occurred during transport, storage, and installation of pipes. Failure to take into account the possibility of these damages in the durability models being developed and in the related survival functions makes it impossible to predict the actual durability of these pipes. An analysis of the results also confirmed the thesis formulated on the basis of studies of vitrified clay pipes in Canada that the deterioration of vitrified clay pipes is not age-dependent when the pipes are properly designed and installed, with no damage during installation.