Risk-Based Approach to Evaluate the Reliability of a City Sewer Network

Abstract

Introduction. The authors pay attention to the fact that there exist such technical objects, the reliability evaluation of which — if performed with the use of measures of the “classical” reliability theory (in particular, reliability function and/ or mean operating time to failure) — is ambiguous and poorly interpreted physically. A city sewer network can serve as an example of such an object. The authors consider a situation when the result of the formal sewer network reliability analysis comes into conflict with the physical interpretation of object operation. This generates a need for searching for a more informative reliability indicator peculiar to a city sewer network. Methods. The research is based on the sewer network decomposition-equivalenting method (DEM) developed previously. This method, in turn, is based on the probability theory, reliability theory and mathematical statistics. A database containing the information about all network elements’ failures and restorations over a preceding period, is used as reference material. Results. Operational risk is taken as the reliability measure of a city sewer network. It is defined as the relative volume of sewage, not delivered to treatment facilities of the network due to failures of its elements, in a certain time. A procedure for the quantitative calculation of this measure is developed. Its comprehensiveness and informative richness are demonstrated. The article shapes possible ways of using the “operational risk” indicator when developing a city sewer network renovation strategy. Conclusion. Operational risk as the reliability measure can be used in practice to improve the performance of a city sewer network.

Modeling and Monitoring of Structural Safety of Long-Operating Underground Structures of the Sewage System in the Conditions of Increasing Anthropogenic Actions in Order to Provide Sustainable Lifecycle of Engineering Infrastructure of the Megacity (The Experience of St. Petersburg)

“…At development of big cities unique underground sewage structures require special protection against anthropogenic actions. Sewage pump stations and tunnels as the facilities of an increased level of responsibility should meet the requirements of safe operation excluding the risk of emerging dangerous failures [1,2]. The analysis of data on a current technical state of large pump stations (the depth of loweringdown to 71 m, the diameter -up to 66 m) and deep sewage tunnels (the total length -more than 2500 km) in more than ten largest cities of Russia with developed historical downtowns allowed developing methods of evaluation of their technical state, make a classification and a catalogue of defects.…”