COMBINING CORROSION AND STRUCTURAL PERFORMANCE OF CONCRETE SEWERS: IMPLICATIONS FOR PIPE DESIGN AND REMAINING LIFE

摘要

Concrete sewer deterioration due to biogenic acid corrosion is a serious problem. Sewers are generally gravity systems flowing partly full and dependent on gradient to ensure their effective operation. As they are invariably placed below all other services, any problems with sewers affect everything above them. In congested cities with limited surface space, digging trenches to replace deteriorated pipelines is costly and disruptive. Recent research has extended the Life Factor Method for predicting sewer corrosion to various other cement types. This has led to a better quantification of service life, the design of pipes with thinner walls, and more cost-effective sewers with longer service lives. Over the past few decades, trenchless techniques have been developed for rehabilitating and replacing buried pipelines. These are cost-effective and minimize surface disruption. Before deciding on remedial actions, an assessment of a sewer's performance and condition is needed, to determine how well the hydraulic and structural requirements have been met, and to estimate its remaining service life. Developments with multi sensor inspections provide a complete picture inside sewers, including the quantification of dimensions. Correlating calculated corrosion losses from pipe walls with those measured from multi-sensor inspections and using the resultant wall thicknesses in a structural analysis of the actual loading conditions, provides the input needed to estimate a sewer's remaining life. This establishes the extent and severity of deterioration so that appropriate decisions about remedial measures can be taken. This holistic approach to the rehabilitation of existing sewers and the design and material selection for new sewers will be of significant value in cost-effectively conveying sewage away from the global mega-cities of the future.