| In order to effectively accommodate the recent rapid urban development and infrastructure growth requirements,urban underground utility tunnel has been rapidly developed with the financial and policy support of the state.Nevertheless,at present,the phenomenon of “emphasising construction but neglecting operation and maintenance” in China is widespread with a lack of sufficient management experience in the operation and maintenance phase of the corridor has been responsible for the frequent occurrence of safety incidents.The urban underground utility tunnel bears a substantial number of municipal pipelines and ancillary facilities,and therefore the risk factors that may affect the safety of operation and maintenance are complex and numerous,as well as dynamically changing and transferring to one another over time.Therefore,it is immensely challenging to differentiate the core risk factors,and the safety risks of operation and maintenance of the utility tunnel are unable to be well controlled.Therefore,the question of how to scientifically and systematically assess the safety risks and identify the key risk factors,as well as how to effectively safeguard the safety of the operation and maintenance of utility tunnel has inevitably emerged as a pressing issue.Firstly,with reference to the implications and characteristics of the safety risks of utility tunnel operation and maintenance,as well as based on the principles of risk identification,a list of 27 frequently reported risk factors had been initially selected by utilizing the literature analysis method and combining with the investigation method of experts to add,subtract or merge risk factors to effectively identify the safety risks of utility tunnel operation and maintenance.A total of 23 risk factors in 5 sub-systems which consist of the corridor body,corridor pipeline,operation and maintenance equipment and facilities,environmental factors and management factors have been included.Secondly,taking into consideration the complexity,uncertainty,non-linearity and dynamism of the safety risk system of utility tunnel operation and maintenance,in order to effectively depict and analyse the changes of the safety risk system of utility tunnel operation and maintenance,the Dual Probabilistic Linguistic Fuzzy Cognitive Map(DPLFCM)is formulated on the basis of the fuzzy cognitive map model,and its definition,structure and inference mechanism are elaborated.Simultaneously,by utilizing the S utility tunnel as an illustration,the DPLFCM model of the S utility tunnel’s operation and maintenance safety risks was established by identifying four components which compose concept nodes,association relationships,association weights and initial state values.Thirdly,in view of the inter-coupling of safety risks in the operation and maintenance of utility tunnel as well as the fact that the DPLFCM network is a directional weighted network,six risk node importance evaluation indicators which are applicable to the DPLFCM network are being designed in terms of the network’s local properties and global properties.These indicators comprise risk intensity,outgoing risk intensity,incoming risk intensity,weighted agglomeration coefficient,intermediate risk intensity and proximity risk intensity with reference to the key node identification theory of complex networks.On this basis,a PROMETHEE II-based network node importance evaluation model has been successfully established by integrating the combined assignment method.Concurrently,the above model was applied to the S-utility tunnel to effectively filter out three key risk factors:information level,safety awareness and inter-pipeline interaction.Lastly,on the basis of the reasoning mechanism of the DPLFCM model of the S utility tunnel O&M safety risk,a simulation analysis of risk control countermeasures aimed at key risk factors has been undertaken.The simulation results revealed that in the initial state of the system,the safety value of the S utility tunnel O&M gradually declines over time,indicating that there are concealed threats in the future O&M of the utility tunnel.At the same time,the steady-state values of O&M safety simulated under three simulation scenarios,namely,reducing interactions between pipelines,enhancing the level of information technology and increasing safety awareness,all exhibit different degrees of improvement in comparison with the steady-state values in the initial state,verifying that the risk control measures based on key risk factors are effective in enhancing the O&M safety of the S utility tunnel.In addition,the critical risk factors primarily affect the safety of utility tunnel O&M through factors such as influencing the qualification rate of pipeline valves and fittings installation,the professional level of management personnel and the reasonableness of emergency plan preparation.Therefore,safety awareness plays the most vital role in the safety of the utility tunnel in the early stage of the operation and maintenance phase while the interaction between pipelines possesses the greatest impact on the safety of the utility tunnel in the middle of the operation and maintenance phase and the level of information technology poses the greatest impact on the safety of the utility tunnel in the late stage of the operation and maintenance phase.As such,on the basis of the above outcomes,the risk control recommendations for the operation and maintenance of this utility tunnel will not only enrich the theoretical knowledge of the operation and maintenance safety of the utility tunnel but also serve to perfect the management mode of the S utility tunnel thus offering reference and useful lessons for other utility tunnel projects so as to safeguard their operation and maintenance safety. |
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