| Chemical industrial parks(CIPs)are the main development pattern to promote the integration and upgrading of industry chain and to produce significant benefits of scale.However,the massive scale of hazardous materials and chemical installations bring huge risks.If an accident occurred in a CIP,which easily triggers the escalation of accident chains,resulting in domino effects.In recent years,natural hazards occurred frequently,once natural hazards impact chemical installations,easily causing technological accidents(e.g.,leakage of hazardous materials,fires,explosions).Those accidents are so-called Natech(Natural Hazards Triggering Technological Disasters)events,raising the great attention of governments.The escalation possibilities of Natech events become a new research topic in the academic field.Flood disaster is the main cause of Natech events,many CIPs are located in the coastal areas,for which the potential risk of flood-Natech domino effects is inevitable.Therefore,the study of flood-Natech domino effects risk and the resilience enhancement strategy of CIPs are of great significance with respect to theory research and practical application.Although Natech domino effect is a new topic in the field of process safety,there is no general theory to describe and characterize the phenomenon of concurrent multiple disaster factors and complex accident evolution.The present study on flood-Natech events seldom considers the change of flood parameters and the possibility of multi-source accident escalation.Many studies of domino effects are focused on the escalation of a single technological accident,neglecting the complex phenomenon of the temporal coupling effects of different types of escalation vectors.Moreover,the flood hazards may lead to the failure of safety measures,thus the original prevention & control strategy of domino effects is hard to perform as expected.To this end,this paper selects the flood-Natech domino effects as the research object,takes uncertainty reasoning as the main research mean,and aims at the whole resilience enhancement of CIPs,the following studies are carried out:(1)Study on the evolution mechanism of flood-Natech domino effects.The evolution mode and law of Natech domino effects are explored,basic elements and magnitude scale of the evolution of Natech domino effects are defined,and the characteristics of propagation chains are clarified,describing the Natech domino effects in a general way.For flood-Natech events,statistical analysis for historical accidents is presented on the basis of retrieved data from foreign official industrial accident databases.The categories of high-vulnerability equipment,damage modes and accident scenarios in flood-Natech events are highlighted,supporting the analysis of primary scenarios for possible domino effects.The flood-Natech domino effect is divided into three stages,and a basic analysis framework for flood-Natech domino effects is developed.The basic framework could be dynamically advanced by considering the state transition of chemical units.The potential sources of uncertainties in the application of developed framework are clarified.Those findings could provide theoretical basis for the subsequent chapters.(2)Study on quantitative risk assessment of flood-Natech domino effects.To address the gap that neglects flood-Natech domino effects in current area quantitative risk assessment(QRA)studies,the QRA procedure for flood-Natech domino effects is developed.The limit state equations for three types of high-vulnerability chemical equipment exposed to a flood are established.The fragility model is developed by a machine learning logistic regression algorithm.The change of flood parameters due to the flood-flow over multi-row installations is estimated by Computational Fluid Dynamics(CFD)simulation,the results are used to improve the fragility model,providing more accurate data input for QRA.The numerical method considering multiple risk factors for the calculation of total failure frequency of chemical unit and the risk indicators model are proposed.The case study showed a significant increment of the CIP risk level due to flood-Natech domino effects.The QRA results could provide data supporting and numerical criteria for the strategy of resilience enhancement.(3)Study on the identification method of key units within flood-Natech domino effects.For the deficiencies to depict the higher-order propagation of cascading accidents by numerical method and the limitation of past studies neglecting the concurrent scenarios of multiple accident types within accident propagation,the complex scenario combination of flood-Natech domino effects is depicted using chain event graph.Four possible synergistic effects within the domino accident propagation and the coupling damage mechanism of escalation vectors are explored,and the high-precision methods for the estimation of escalation probability are established.The identification method of key units within flood-Natech domino effects is developed.Specifically,Bayesian Network(BN)is used as the tool for modeling and quantifying uncertainties,and the influence of synergistic effects and ignition modes on accident escalation is taken into account,allowing more accurate calculation for domino scenario probability.The importance indicator is proposed to identify the key units with the huge impact on accident evolution,which could be verified by the sensitive analysis of BN nodes,providing theoretical support for the identification of high-priority units in CIP resilience enhancement strategy.(4)Study on the accident prevention performance of safety barriers with respect to flood-Natech domino effects based on quantitative resilience.For the research difficulties of the dynamic transitions of equipment unit and safety barrier states within cascading accidents,the general resilience assessment model based on resilience process is expanded,supporting the development of the assessment method of accident prevention performance of safety barriers based on quantitative resilience.The action mechanism and effects of safety barriers within flood-Natech domino effects are studied,and the interactions between hazards,chemical installations and safety barriers are explored.The system state transition model and evaluation functions for resilience are developed.Taking the Dynamic Bayesian Network(DBN)as the main tool,the chemical unit state is dynamically predicted to solve the evaluation functions for resilience.The application of the developed method evidenced that the configuration of safety barriers with the best accident prevention performance could be identified by the comparison of resilience curves,which provides the theoretical basis for the construction of barrier system in the resilience enhancement strategy.(5)Study on the resilience enhancement strategy of CIPs for coping with flood-Natech domino effects.By introducing the general resilience concept based on resilience factors in the field of process safety,the characteristics of CIP resilience are illustrated from the time scale,and four principles of resilience enhancement are proposed.It is pointed out that the resilience enhancement strategy of CIP should be considered from both technological and organizational dimensions.In the technological dimension,the general model of a barrier system coping with flood-Natech domino effects is proposed.Focusing on the goal of establishing and improving the barrier system,the whole period technological resilience enhancement framework is developed on the basis of risk acceptance criteria and barrier management principles.In the organizational dimension,the CIP management structure is established based on the safety cycle,and the responsibility of government,CIP and enterprise are explained respectively.The whole period organizational resilience enhancement framework for CIPs is further proposed.Both developed frameworks could integrate the former studies in an effective way,driving the improvement of CIP safety level. |
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