| Due to the long construction period of the tunnel project,many uncertain factors,complex construction technology and large investment,safety accidents frequently occur during the construction of highway tunnels.In particular,shallow buried unsymmetrical pressure highway tunnels are deeply affected by factors such as topography and geology,excavation methods,and supporting lining conditions.During the construction process,it is very easy to fall off the surrounding rock at the face of the tunnel,collapse the opening,crack the surface and supporting structure deformation and other issues.By conducting risk assessment and control research on the construction risks of shallow buried unsymmetrical pressure tunnels on mountain highways,it is helpful to reduce the level of construction risks,reduce risk losses,and make project decision-making more scientific and rational.Based on the research background of the Swan Cave Tunnel construction project of Zheng-Xi expressway,this paper conducts identification,analysis,evaluation and control research on the construction risks of shallow buried unsymmetrical pressure tunnel on mountain highways by consulting a large number of related literature and books.The main contents are as follows:(1)By summarizing,comparing and analyzing risk identification methods and risk assessment methods,combined with the characteristics of mountain highway tunnel construction,the construction risk identification method of Swan Cavern tunnel is clarified: the work structure-risk decomposition method is combined with the improved expert investigation method.The fuzzy analytic hierarchy process and the improved Monte Carlo simulation method are used to establish a risk assessment model to obtain the level of construction risk.(2)According to the characteristics of Swan Cave tunnel construction and excavation,establish a working structure decomposition tree(WBS);from the perspective of "human-machine-environment-materials",the potential risks in the construction process are decomposed,and a risk structure decomposition tree(RBS)is established,combine the two to create a WBS-RBS matrix.On the basis of the constructed matrix,combined with the actual situation of the project and the discussion of the review team,the risk factors were screened to establish a risk index system for the construction of the Swan Cave tunnel.By improving the expert survey method,the "confidence index method" is used to score and optimize the expert survey results.(3)The fuzzy analytic hierarchy process is used to evaluate the construction risk of Swan Cave tunnel.When using the analytic hierarchy process to determine the weights of risk factors,the risk assessment model based on analytic hierarchy process judgment matrix is established by combining MATLAB software and analytic hierarchy process,which can greatly simplify the calculation.The improved analytic hierarchy process is used to optimize the judgment scale and consistency judgment of the judgment matrix,and the weight ranking of various risk factors in tunnel construction process is obtained.By collecting and sorting out the occurrence probability and consequence loss value of each risk index,the Monte Carlo simulation method is used to for computer simulation,and the risk consequence model is established.The two are combined to establish an improved Monte Carlo evaluation model.(4)The fuzzy analytic hierarchy process and the improved Monte Carlo simulation method are used to analyze and evaluate the construction risk of the Swan Cave tunnel.The overall construction risk level of the Swan Cave tunnel is three,and the necessary risk treatment measures are needed to reduce the risk level.Effective avoidance measures and response plans are proposed for the risks with higher levels of pregnancy insurance,and the consequences of risk loss are controlled within an acceptable range. |
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