Research On The Identification Of Safety Risks And Its Evolution Law Of Metro Shield Construction

In recent years,China’s urban metro construction process has been accelerated,and the number of cities constructing metros has gradually increased.The shield method has become the main construction method of urban metro tunneling projects,and the safety accidents during the metro shield construction period also show a frequent occurrence,resulting in serious economic losses,casualties and adverse effects.The intrinsic dynamic nature and uncertainty in the construction process of the shield tunneling,making the safety disaster mechanism complicated with multi-source risk factors.Thus,it is important to explore the mechanism of safety accidents during the shield tunneling process and analyse the characteristics and laws of its construction safety risk evolution to control the evolution of safety risks and prevent accidents from occurring.In view of this,this thesis takes safety risk during the metro shield construction period as the research object,and uses complex network theory and successive failure theory to study the interaction relationship between risk factors and risk evolution propagation process.And the key risk factors are obtained and their the characteristics and laws of construction safety risk evolution are identified.The main research contents are as follows:(1)Based on the relevant studies and normative standards on safety risks of metro shield construction at home and abroad,this paper adopts the WBS-RBS method to systematically and comprehensively identify 55 initial risk factors.By collating domestic and international metro shield construction accident cases from1981 to 2022,establishing a risk transfer chain,judging whether the identified initial risk factors have the possibility of risk occurrence,sifting through them,summarising46 risk factors and constructing a metro shield construction safety risk factor index system.At the same time,the underground shield construction accidents were summarised into 12 types of risk events.(2)In view of the non-linear and complex relationship between risk factors of metro shield construction,risk factors as network nodes and interrelationships between risk factors as network connecting edges in this paper,a risk evolution network model is constructed.The important characteristic indexes of the network model are analyzed to explore the characteristics and laws of metro shield construction safety risk evolution.(3)On the basis of the analysis of the network model for the evolution of safety risks in metro shield construction,ideas and analysis tools such as multi-attribute decision making and simulation are used to simulate the global efficiency of the network with different metrics under random and deliberate attacks,and to identify key risk factors.In order to further reveal the influence of the interaction relationship between risk factors in the formation process of metro shield construction accidents.The risk transmission evolution model for metro shield construction based on the successive failure theory and risk propagation dynamics is established.With key risk factors as the benchmark,the risk evolution propagation process are simulated,and the most likely formation of risk transmission evolution path are find out.The risk assessment of risk transmission evolution path is evaluated,and countermeasures are proposed for the pre-control of safety risks in the construction of the metro shield method.