Construction Risk Assessment And Safety Pre-warning System Design For In-situ Expansion Of The Existing Tunnel

In the 1970s and 1980s,the design of urban highway tunnels in China was mostly two-way four lane.With the continuous progress of social economy and the continuous improvement of people’s living standards,the requirements for highway transportation capacity will become higher and higher,so that the original single lane tunnels in China can no longer meet the needs of transportation capacity and safe driving,which to a certain extent hindered the process of urban development.At the same time,the old tunnels in China are damaged to varying degrees or even cannot meet the normal use requirements,which also makes the reconstruction and expansion of tunnels more urgent,thus making the reconstruction and expansion of existing tunnels gradually become the focus of the engineering community.In the expressway reconstruction and expansion project,the tunnel project,as a controlling node,must receive enough attention.At present,there is little research on the expansion of underground space.The reasonable expansion form and process are related to the project safety,investment scale,etc.As an important topic in the field of tunnel engineering,the tunnel reconstruction and expansion will gradually enter the mainstream.At the same time,the existing tunnel reconstruction and expansion project is a highly technical and professional project.Compared with other projects,its construction process has significant characteristics such as large project volume,complex process,strong dynamic coordination and low information transmission efficiency.These characteristics have brought many potential risk factors to the project construction management and are very likely to cause safety production accidents,which puts forward greater challenges and higher requirements for all parties.How to systematically and comprehensively identify the influencing factors of construction safety risks,accurately and timely conduct dynamic risk assessment,scientifically and reasonably take technical measures for risk control,and be able to conduct dynamic monitoring and control,so as to control the deformation of tunnel reconstruction and expansion itself and the deformation of existing tunnels,is an urgent problem to be solved for such projects.Therefore,the research on the safety problems in the construction phase of the existing tunnel reconstruction and expansion project has become an important direction of the development of the construction industry.At the same time,the research on the construction safety risk control of the municipal tunnel reconstruction and expansion project has great practical significance and broad application prospects.Based on the first in-situ expansion tunnel of the original site in China,the second and fourth expansion project of the Loushan Tunnel in Zhejiang Province,this paper comprehensively uses Analytic Network Process,Extenics theory,and BIM technology to carry out the research on the construction risk assessment and safety early warning system design of the in-situ expansion project around the existing tunnel.The main research contents and achievements are as follows:(1)Analysis and identification of risk factors in the in-situ expansion of the existing tunnelsCombined with the construction characteristics of the expansion project around the existing tunnel,this paper systematically expounds the relevant theoretical background of the construction risk assessment of the expansion tunnel project,and analyzes the construction process risk of the in-situ expansion project of Loushan Tunnel.Firstly,the process of risk and risk management as well as the identification principle,assessment process and method of risk factors are discussed,the scale of probability of risk assessment,the grading standard of consequence grade and acceptance criteria are described,and common risk response strategies are proposed.At the same time,the paper introduces the construction risk of existing tunnel expansion project,and the characteristics of the in-situ expansion tunnel different from the general new tunnel,discusses the rules of the construction accident risk of the in-situ expansion tunnel,and determines the research basis of the construction risk factors of the in-situ expansion tunnel.Then,according to the existing technical data,the impact of multiple overlapping and risk factors is evaluated,and the different risk factors formed during the expansion construction around the existing tunnel are refined,which are: the existing tunnel status,geological conditions,construction technology and monitoring measurement factors.At the same time,17 risk factor indicators under the condition of multi-level risk superposition are analyzed and summarized,which provides a theoretical basis for the use of ANP to determine the weight of risk factors.(2)Risk assessment index for the in-situ expansion of the existing tunnels based on ANP methodComprehensively considering the internal circulation of the control layer and network layer structure of the existing tunnel in-situ expansion construction process,as well as the dependence and feedback between the hierarchical structures,first of all,on the basis of the evaluation method of the previous researchers using the analytic hierarchy process,combined with the risk factors of the 17 municipal tunnel in-situ expansion around the construction extracted in the previous chapter,a risk evaluation index system consisting of 4 first level indicators and 17 second level indicators was established.Then,ANP is used to improve the existing evaluation index system and establish the risk network structure model of municipal tunnel in in-situ expansion construction.Then,each risk factor is compared in pairs to build a judgment matrix.With the help of operation software,the super matrix,weight matrix,weighted super matrix and limit super matrix are output in turn.Combined with the external weight and internal weight of all elements,the mixed weight of each indicator element is obtained through comprehensive analysis,so as to calculate the weight of each risk,and finally the weight ranking of each risk factor is obtained,It provides data reference for further comprehensive network analysis and Extenics evaluation of risk level.(3)Risk assessment model for the in-situ expansion of the existing tunnels based on ANP-ExtenicsThe comprehensive network analysis method and Extenics theory are comprehensively applied to the risk assessment of the reconstruction and expansion process of Loushan Tunnel.Through the established evaluation system of the construction risk indicators for the expansion of municipal tunnels around the site,and on the basis of the safety evaluation indicator network structure model and weight calculation established in Chapter IV,the comprehensive evaluation model of the construction risk for the expansion of municipal tunnels around the site based on ANP Extenics is constructed,This paper studies the risk assessment of the construction of the existing tunnel in situ two expansion and four expansion.On the basis of Extenics theory,the basic principle of network analysis method is introduced,the concept of ANP Extenics model is proposed,and the basic idea and steps of establishing ANP Extenics model are described in detail,so as to provide a new method of solving complex problem decisionmaking.Through example verification,based on matter element theory and Extenics transformation principle,the correlation degree and evaluation grade of factor indexes to evaluation grade are obtained.According to the calculation results of the correlation function and correlation degree of the risks of the index layer and the target layer,the construction safety risk assessment of the the in-situ expansion of Loushan Tunnel is "relatively safe".The results show that the ANP-Extenics model based on Extenics and ANP can truly reflect the uncertainty in the risk assessment process of the the in-situ expansion of Loushan Tunnel,which proves that the model has good application for tunnel construction safety assessment.(4)Pre-warning system design for the in-situ expansion of the existing tunnels based on BIMAiming at the problems of BIM technology in tunnel modeling,such as heavy workload,low model accuracy,and non intuitive safety early warning,relying on the reconstruction and expansion project of Loushan Tunnel,this paper proposes and successfully demonstrates the intelligent construction of tunnel BIM model and the research on visual pre-warning system design.On the one hand,based on the Autodesk platform,a number of software collaboratively and effectively completed the intelligent construction of the Loushan Tunnel BIM model.Civil 3D+Revit+Dynamo were used to build the intelligent tunnel BIM model,realizing the goal of integrating advantages,rapid modeling,and improving modeling accuracy.At the same time,the problem of data loss and model defect during the transmission of different software design results was avoided.On the other hand,based on the interaction between the Dynamo plug-in and Excel,the monitoring and measurement database in Excel format can be accurately read by the Dynamo plug-in.Use Python script to write displacement management level identification program independently to expand the function of Dynamo node.According to the actual monitoring displacement of the Loushan Tunnel,the risk level color module is divided,and the read and determined risk levels are displayed on the tunnel model structure section to complete the pre-warning system design.The intelligent construction of tunnel BIM model and the application of visual early warning have improved the information integration degree for the in-situ expansion of Loushan Tunnel Project,and provided accurate basis for the schedule adjustment,support parameter change and risk assessment during the construction.