Safety and Risk of Operating Facilities: Rapid Assessment Methodology

Abstract

Two methods for methodology uses “risk indices” (dam condition index I), as well as “fuzzy logic methods” to combine the original quantitative and qualitative (expert) information on the operated dam condition. The approach applied is in accordance with the recommendations of IEC 31010: 2019. Risk Management — Risk Assessment Techniques. Deterministic assessments of the condition in the form of “risk indices” were also used as input data in assessing the probability of the failure and in developing a probabilistic risk assessment methodology. The original database, as well as the damage assessment scale, modified in the course of the research, summarize the experience of surveys and examination of safety declarations of more than 180 hydraulic works in Russia. A description is given of the methods of initial assessment and digitization (quantification) of the condition index I, as well as combining the initial quantitative and qualitative (expert) information about various damages. The practical feasibility and the possibility of categorizing (with fuzzy boundaries) conditions and levels of damage to hydraulic structures are shown. With regard to various conditions and levels of damage, proposals are made for practical actions to ensure the safety of dams in the process of monitoring, inspection, development of a reconstruction project and its expertise. As a result of the research, the dependence of the probability of the failure pfailure on the average value of the Iср index has been established and the graph “pfailure – Iср” is presented, which is well described by the exponential and is convenient for practical application. The value of I ср is determined according to the data of visual and instrumental control of the dam condition of the as well as according to expert estimates. The methodology for creation the indicated graph is presented. The creation of this graph became possible on the basis of: statistical processing, proof of the “normality” of the distribution of the I indices and the estimation (according to the distribution functions constructed for each level of damage) the probability of the failure pfailure, as well as during the survey and examination of the dam project. Proposals are formulated for the practical application of the proposed methods for assessing the risk of operating dams, and the near-term prospect of research in the field of risk assessment and ensuring dam safety is formulated.