Safety Risk Assessment And Control Of Deep-Water Foundation Construction Of Long-Span Cable-Stayed Bridge Based On Improved Evidential Bayesian Network

Cable-stayed bridge is the main type of bridge crossing various obstacles such as rivers,lakes,canyons and mountains.It has the advantages of large span,simple force bearing and magnificent appearance.Cable-stayed bridge has achieved rapid development in recent years and is widely used in long-span bridges,which has also aroused the public’s attention to its construction safety issues.The deep-water foundation of longspan cable-stayed bridge is the key load-bearing structure built in deep-water areas.Its construction is very sensitive to environmental changes,and has the characteristics of deep-water operations,numerous processes,ship navigation,and long construction periods,resulting in a large number of uncertain construction safety risks.As the main span of long-span cable-stayed bridge increases and the depth of deep-water foundation increases,construction safety risk becomes more and more complex,resulting in higher and higher requirements for risk assessment and control in engineering practice.However,the existing theoretical research on safety risk management of deep-water foundation construction of long-span cable-stayed bridge is relatively weak,which does not meet the urgent needs of risk management guidance in engineering practice.Therefore,it is of great theoretical significance and practical value to conduct research on the safety risk assessment and control of deep-water foundation construction of long-span cable-stayed bridge based on the improved evidential Bayesian network.It not only helps to improve the safety risk management theory of deep-water foundation construction of long-span cable-stayed bridge,but also helps to guide the safety risk management of deep-water foundation construction of long-span cable-stayed bridge in engineering practice.First of all,this thesis deeply studies the construction safety risk characteristics determined by the technical and economic characteristics of deep-water foundation construction of long-span cable-stayed bridge.After literature research,expert consultation and construction technologies,based on the 4M1 E theory and the accident causation theory,the safety risk list for deep-water foundation construction of long-span cablestayed bridge is constructed from the five dimensions of operator factor risk,mechanical and material factor risk,management factor risk,construction technology factor risk,and environmental factor risk,and their internal logical relationships are revealed.Secondly,the improved evidentical Bayesian network risk assessment model is constructed based on the improved cloud model with optimal cloud entropy,improved evidence theory,the definition of "risk state contribution value" and Bayesian network,which not only takes into account the characteristics of fuzziness,randomness and uncertainty in the safety risk assessment of deep-water foundation construction of long-span cable-stayed bridge,but also takes into account the subjectivity of experts,the difference of expert subjective cognition and the efficiency of expert decision-making,etc.The model adopts the improved evidence theory to improve the prior probability of Bayesian network,and uses the definition of "risk state contribution value" to improve the conditional probability of Bayesian network.Then the risk level and the key risk factors are determined by Bayesian network bidirectional reasoning and sensitivity analysis.Thirdly,based on risk control theory and construction safety theory,safety risk control measures for deep-water foundation construction of long-span cable-stayed bridge are put forward from the perspectives of safety risk control such as operator factor risk,mechanical and material factor risk,management factor risk,construction technology factor risk,environ-mental factor risk.Finally,the improved evidence Bayesian network risk assessment model is applied to the deep-water foundation engineering case of the 2# and 3# main tower piers of a Yangtze River Bridge in Fengdu District,Chongqing.The research results are consistent with the actual engineering situation,thus verifying the feasibility and effectiveness of the risk assessment model.The study provides references and help for the safety risk management of deep-water foundation construction of long-span cablestayed bridge in engineering practice.