Research On Construction Risk Of Subway Deep Foundation Pit Based On Improved Fuzzy Comprehensive Evaluation Method

Urbanization of China has been developed rapidly in the past few years.Because of the increasingly traffic pressure,many cities have begun to build subway.Deep foundation pit projects of subway usually have some prominent features such as bigger investment,elusive,complexity and uncertainty.Therefore,major engineering accidents frequently occur during the construction process.It always has serious impacts on the construction progress and safety of project.Therefore,detect risks in time and take effective measures in advance can reduce the probability of occurrence and reduce the losses caused by the occurrence of risks.It is of great theoretical and practical significance to do risk assessment for deep foundation pit project of subway.(1)This paper introduces the basic concepts and methods of risk assessment and optimizes the theory of fuzzy comprehensive evaluation method.According to the construction technology and process of open-cut excavation of subway deep foundation pit,the work breakdown structure(WBS)and the risk breakdown structure(RBS)have been established;7 types of risk events and 25 risk factors of the construction have been identified.Take the WBS-RBS combination method to construct,the subway deep foundation pit construction risk assessment index system.(2)The method for calculating the weight values of risk factors for deep foundation pit of subways based on the analysis of the influencing factors of risk assessment of open-cut excavation of subway deep foundation pit.Then a fuzzy comprehensive evaluation model of construction risk assessment of subway deep open-cut excavation method could be established by introducing nonlinear fuzzy matrix synthesis operator and combining with engineering data and the membership degree of risk factors determined by engineering data and expert investigation.(3)In the end,based on the evaluation model,the risk level of specific engineering examples of Donggang Subway deep foundation pit construction is determined to be level 3 which belongs to undesired risk.Then some specific engineering measures are formulated according to the risk assessment results.The dynamic monitoring of the construction process after taking risk control measures shows that the risk events are effectively controlled,which can effectively guarantee the safety of the construction and also verify the effectiveness and applicability of the risk analysis.