Study On The Risk Analysis Model For The Progress Of Shield Underpassing A High Speed Railway Section Under Construction

In recent years,with the gradual expansion of the scale of metro tunneling projects and the increasing number of shield tunneling projects,the problem of tunneling project schedule risks has become increasingly prominent.In order to effectively control the construction progress,it is urgent to conduct a comprehensive and in-depth analysis of the schedule risks of shield tunnel underpassing under-construction high-speed railway sections.The current research on tunnel schedule risks focuses on identifying and analysing the interaction between risk factors,and lacks quantitative analysis of the sensitivity and importance of risk factors as well as the intensity of influence between risk factors.Therefore,according to the construction characteristics of the shield underpassing under-construction high-speed railway section,the construction of a shield underpassing under-construction high-speed railway section schedule risk analysis model has important theoretical value and practical significance for achieving the schedule target of the shield underpassing project.The schedule risk of shield underpassing under-construction high-speed railway section has data characteristics such as fuzzy risk indicators,many risk factors and complex logical relationships,and as schedule risk analysis generally acts in the early stage of engineering projects and project data is incomplete,a Bayesian network based on fuzzy fault tree is adopted as the schedule risk analysis model.Combining the advantages of fault tree,fuzzy theory and Bayesian network,a fuzzy Bayesian network schedule risk analysis model is established for the shield underpassing the under-construction high speed railway section.In this paper,the following research is conducted on the construction schedule risk of shield underpassing the under-construction high-speed railway section:(1)Taking the construction of a shield tunnel underpassing an under-construction highspeed railway section in a certain region as the research background,and with reference to the characteristics of complex geological environment,difficult construction technology and numerous risk factors of the underpassing under-construction high-speed railway section,on the basis of reference to domestic and foreign shield underpassing railway roadbed construction,risk assessment and schedule risk information,on-site research and analysis of the underpassing section construction important and difficult points,the schedule risk factors of the underpassing under-construction high-speed railway section are screened out.At the same time,questionnaires were administered to the construction units,design units and university experts in relevant fields involved in the underpass section project to optimise the schedule risk factors and identify the main schedule risks of the shield underpassing the under-construction highspeed railway section.(2)Further analysis was carried out to determine the logical relationships between risk events,and logic gates were applied to connect the events in series to establish a progress risk fault tree for the shield underpassing the under-construction high-speed railway section.The research data was collected by combining both on-site monitoring and questionnaire surveys,and the fuzzy failure rate of each bottom event was calculated by defuzzifying the data.The fuzzy fault tree model was transformed into a Bayesian network model through information extraction and reorganisation,and a progress risk analysis model based on fuzzy Bayesian network was constructed for the shield underpassing the under-construction high-speed railway section.(3)The model analysis results show that the shield tunneling risk for the construction schedule of this shield underpassing the under-construction high-speed railway section is the highest,followed by construction management risk and construction environment risk,and the probability of construction schedule delay for the whole shield underpassing the underconstruction high-speed railway section is 36%,with the construction schedule risk at a high level,among which shield attitude deviation,cutter head and tool wear,construction cross interference,hard underground obstacles and soft ground are the sensitive factors leading to shield underpassing The model analysis results were compared with the field monitoring data.The results of the model analysis were validated against the on-site monitoring data,and the results showed that the findings were consistent with the Bayesian network schedule risk model for the shield underpassing the under-construction high-speed railway section,demonstrating the accuracy of the model,which can be used as a reference for similar projects.