Research On Risk Assessment Of Highway Tunnel Construction Period

With the rapid development of construction and transportation in China, the number and size of tunnel construction projects are growing fast. But due to the severity of external environment of engineering, the difficulty of construction and the complexity of participants etc., more and more uncertain factors will have an influence on the period of highway tunnel construction. Catching the time limit for a project disorderly may not only result in the increase in cost, but also cause the inevitable security accidents. Because of the unique character of highway tunnel construction, the risk factors which influence the construction period do not exist in isolation, but in an interrelated and interactive relationship. One of the problems that need an immediate solution for the current researchers is how to identify the risk factors and set up the risk assessment model according to the characteristics of highway tunnel engineering project.Risk assessment is the most important step in risk management. After risk assessment, the manager can do a better risk identification, estimation and assessment, then provide the basis for the later risk pre-control plan. Through the study of the definition and understanding of risk and construction period, this paper, firstly, puts forward the definition of period risk for the highway tunnel construction, and then by the definition, the damages and losses are obtained.Secondly, the introduction of the definition of period risk assessment for the highway tunnel construction is introduced. Risk assessment can be divided into three parts: risk identification, risk estimation and risk assessment. Risk identification is the first step in the time period risk assessment, as well as the most important step. Only after the risk factors are all identified, can the risk estimation and assessment be carried out smoothly. Risk estimation includes the risk probability estimation and loss estimation. The last step is risk assessment. Only after the corresponding risk assessment model of the risk factors is set up, and the risk probability and consequences are sorted, can the basis be provided effectively for the pre-control measures of subsequent risk. The methods of risk assessment can be divided into qualitative method, quantitative method and qualitative-quantitative method. In this paper, three methods are used to evaluate the risk: Data Envelopment Analysis(DEA), Program Evaluation and Review Technique(PERT) and System Dynamics(SD).Thirdly, through the study of instances, Data Envelopment Analysis(DEA), Program Evaluation and Review Technique(PERT), and System Dynamics(SD) are used to assess and model the risks of each link in the project. The optimal plan of the project is determined by DEA. PERT is used to confirm the key path and estimate the completion probability. Employing SD to monitor the risks of highway tunnel construction period: firstly establish the risk identification model for the whole project system with SD, and then assess risks in the construction process through the establishment of a flow diagram.Finally, combined with the analysis of instances, the three methods in period risk assessment for the highway tunnel construction can be found their most suitable stages and characteristics. Through the analysis and comparison of differences, the basis for the choice of assessment methods is provided.With the multiple sources and acting paths of construction period risk as well as its wide coverage, it is difficult to control the whole risk factors with the single assessment method. In this paper, three kinds of assessment methods are adopted to evaluate the project risk in each period, intending to provide a reference for the manager of engineering projects, which is of great theoretical and practical significance.