Risk analysis of embankment dams: application to a tailings dam (original) (raw)
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Springer Tracts in Civil Engineering, 2020
Risk assessment process of dams can be time-consuming and may require high investments. If risk value of every dam is defined, then the resources could be shared more efficiently. Descriptions of evaluation procedures for various failure modes such as piping, flood, earthquake and stability are described in this chapter. Consequence assessment procedures are presented in detail, together with the steps of the risk evaluation process, thus helping to identify the appropriate failure mode for examined dam. Moreover, the evaluation of dam safety failure modes with the appropriate life loss potential procedures is described in this chapter. 3.1 Risk Prioritization of Dams 3.1.1 General Estimated loss of life and damage in downstream from a dam failure are used to create three classes in dam safety regulation studies that are: • High Hazard if probable loss of life is expected; • Significant Hazard if possible, loss of life and major damage is expected; • Low Hazard if no loss of life, minor image is expected. Risk assessment process of dams could be time consuming and need high investments so risk prioritization is an effective alternative for starting to examination. If risk value of every dam is defined then the resources could be shared more efficiently. 3.1.2 Process Outline Process of risk assessment include the most essential failure modes for each type of dam so that overall dam risk can be compared with risk tolerability criteria. The below figure show steps of risk categorization process [36] (Fig. 3.1).
Safety of Dams: A Pathological Approach of Qualitative and Quantitative Risks
Journal of Civil Engineering and Architecture, 2016
Dams are critical and essential elements in any infrastructure and, in front of accidents occurred in many countries, it is extremely important to know the risk of these structures. Inserted in this context, it was found in the technical literature, methods and tools capable of measuring the exposure value by means of indicators. In the study, the highlights were 12 methods of qualitative, semiquantitative and quantitative risk analysis, representing an overview of risk analysis methods available in the literature with potential use in dams, that it has been done into electronic spreadsheets. The case study is performed on a sample of concrete dam and earth/rockfill built and operated by Eletrobrás Furnas Company, supported by documentary research, projects, field inspections and interviews with experts. After applying the methods and the analysis thereof, has been prepared the Eletrobras Furnas dam risk analysis method which is characterized by adapting the criteria analyzed to the reality of the company's dams and it was also performed the portfolio risk analysis of 18 dams. In spite of the variety and subjectivity of qualitative and semiquantitative methods, the results show that they tend to converge on the analysis of dam based on risk. The application methodology demonstrates the feasibility assessment stage, covering the preliminary analysis for portfolio dams, followed by formal and individual risk analyzes for the most critical structures. These results confirm the applicability of risk analysis techniques, contributing to the consolidation of this tool as fundamental in the dam safety.
Risk Management Concepts in Dam Safety Evaluation: Mosul Dam as a Case Study
Gradual shift has been observed lately of dam safety procedures from the conventional technical based towards a wider scope of risk management procedure based on risk analysis. The new approach considers the likelihood level of occurrence of a multitude of hazards and the magnitude of the resulting possible consequences in case of failure using rational cause and effect arguments. Most dam owners are shifting towards the use of the new risk based procedures; and even governments themselves are moving towards formalizing the new trend. Legislations in the United States were promulgated [1] after serious dam failures and the adoption of stringent levels of scrutiny led such federal dam owners to pioneer in this field and in developing the concepts and methods required. The corner stone in risk analysis is the definition of the potential modes that may lead to failure and assessment of the likelihood levels of their occurrence and possible category of the consequences which, after thorough evaluation, will shape the decision making. This type of analysis was applied to Mosul Dam as a case study and resulted in definite recommendations.
Natural Hazards, 2014
Failure modes for earth dams are extensively reviewed and analysed using a three-pronged approach including a literature review, physical observations of a representative earth dam site and finite element structural analysis of the dam wall. Several failure scenarios are used for predicting consequences in terms of downstream inundation and damage. The fluid flow component is performed using the mesh-free smoothed particle hydrodynamics method. For a representative earthen dam, piping and landslip are identified as key failure modes based on a combination of finite element analysis, theory and physical observations. Inundation behaviour is very different for the two failure modes. The landslip failure is the most critical one for the dam studied with flood water breaking the river bank and affecting surrounding property and farmland. For the piping failures, water flow from the initial pipes formed for significant periods before they collapse, but the flow rates are small compared with that of the much larger landslip mode. After failure, fragments of the collapsing wall block the breach and can considerably restrict the flood discharge. In some cases, the water pressure is able to push the obstructing material downstream and some minor flooding occurs, but in others cases the breach can remain blocked with little flooding occurring. A prototype risk framework is developed using the small database of the pre-computed flooding scenarios and key variables that affect inundation such as water level in the reservoir. This can be used to estimate inundation maps for as yet non-computed scenarios through interpolation and superposition techniques. The implementation of the risk framework is demonstrated by the estimation of inundation maps for two in-between non-computed reservoir levels. Inundation due to multiple breaches is also estimated by superposition of three single-breach scenarios. Results are compared against the simulated multiple breach. A preliminary implementation of this risk framework into a geographic information system is also described.
Modified risk assessment tool for embankment dams: case study of three dams in Turkey
Civil Engineering and Environmental Systems, 2017
Dam failures are catastrophic accidents resulting in property damage and loss of life. Risk prioritisation systems should be used in accordance with dam safety regulations to prevent these disasters. The purpose of this paper is to develop a risk assessment software which can be used by the decision makers for ranking of dams. Risk assessment was conducted on three embankment dams from Turkey to obtain information about the dam performance based on piping, earthquake, normal stability and flood failure modes. Parameters are incorporated into the programme to develop a new model that could predict variables such as breach width, dam failure time, side slope and peak breach discharge. The proposed tool gives flexibility to choose dam elements for describing the primary features of the evaluated dam; so users can make hazard categorisation of dams according to their risk level which is based on unique project conditions.
Risk assessment and dams – Recent developments and applications
2019
Increasingly, society and standards require "risk-informed" decisions. The paper demonstrates the benefits of implementing reliability and risk concepts in dam engineering as a complement to conventional deterministic analyses. Reliability evaluations can range from qualitative estimates, to simple statistical evaluations, to full probabilistic modelling of the hazards and consequences for a system of dams. The paper gives an overview of basic concepts of reliability-based approaches and illustrates their use with three case studies. The paper discusses the strengths of reliability-based analyses and key issues such as tolerable and acceptable risk, the meaning of factor of safety, the targets for a margin of safety and the selection of characteristic value for analysis. Reliability-based approaches provide useful insight and complementary information. They enable the analysis of complex uncertainties in a systematic and more complete manner than deterministic analyses alo...
RISK ANALYSIS FOR DAM SAFETY EVALUATION: HYDROLOGIC RISK
This report was initiated under the U.S. Army Corps of Engineers' Dam Safety Research Program. The report was prepared to fulfill part of several work units in the research program. These work units focused on outlining dam safety standards, developing risk and uncertainty concepts, and specifically studying aspects of risks of failure involving dams and spillways constructed by the Corps.
Tailings dam scenario: knowing to avoid new catastrophes
Ambiente & Sociedade
Mining is one of the key sectors of the Brazilian economy. However, despite its importance, tailings production is still significant and constitutes one of the greatest problems in this sector. Moreover, dam failure events have marked the history of the mining sector. From this perspective, this study aimed to assess the current scenario of tailings dams based on information contained in the SIGBM database. First, the number of dams included in the PNSB, their risk categories, potential damage, level of emergency, and other factors were observed. Then, data analysis indicated that Minas Gerais is the state with the largest number of dams included in the PNSB, with high CRI and DPA, dam construction by the upstream method, and dams classified as emergency level 3, thus requiring extra attention and interventions in order to ensure their safety.
FAILURE MODES APPROACH TO SAFETY EVALUATION OF DAMS
Seismic performance of concrete dams is currently conducted on the basis of stress checks combined with engineering judgments. The paper introduces a failure modes approach for assessment of seismic safety of dams. Although this approach still uses magnitudes of stresses as a cursory measure of the performance, safety of the dam is assessed on the basis of potential modes of failure that could occur. The goal of the seismic safety evaluation is therefore to conduct appropriate analyses and evaluations that could demonstrate whether or not certain failure modes can develop.