Research And Application Of Shield Construction Environmental Risk Assessment Method Based On Engineering Data

In recent years,shield method has been widely used in tunnel construction with its advantages of high automation,fast tunneling speed and strong adaptability to complex environment.At the same time,the shield method will bring many risks and hidden dangers,such as high construction risk,difficult control,dynamic development of risk,and ground disturbance caused by passing through the building.In view of this,this thesis takes the shield tunnel construction project of the left line in the north extension project of Tongjing Road in Suzhou as the background,and uses data intensive scientific research methods and ideas to explore the dynamic risk assessment method in the shield construction process.In this thesis,the environmental risk assessment index system is determined,and the decision tree classification model of environmental risk assessment of shield construction method is constructed,and the dynamic assessment process of environmental risk is improved.Furthermore,this thesis takes Bao ’en Temple as a paradigm,and the research results can be applied to the protection of ancient buildings in the construction of right line tunnel,providing reference for the dynamic assessment of environmental risk in subsequent similar projects.The specific tasks completed are as follows:(1)Based on the shield tunnel construction project of the left line in the north extension project of Tongjing Road in Suzhou,this thesis summarizes the types of environmental risk sources along the construction line,selects the environmental risk of buildings as an example to elaborate the reasons why ancient buildings are more dangerous than general buildings during shield construction,and lays the foundation for the exploration of environmental risk assessment methods with the initial purpose of protecting ancient buildings in shield construction.According to the original engineering data and structure,the extraction and preprocessing of data required for the study of ground settlement,building settlement,etc.are completed through Python language and data cleaning to provide data support for this study.(2)The method of constructing a whole process wrapped environmental risk assessment index system according to the risk-causing process of environmental risks in shield construction is proposed.According to the research methods and ideas of data intensive science,the law of engineering monitoring data is studied by using box-plot.According to the research results,the characteristic distribution relationship of each index is clarified,and the classification level of each index is determined.(3)The idea of applying decision tree classification method to risk assessment is put forward and the suitability analysis is carried out.In this thesis,it is creatively proposed that the whole process wrapped environmental risk assessment index system can be directly used as the attribute of decision tree through transformation,which eliminates the process of attribute selection in traditional decision tree model construction,and improves the efficiency and engineering practicability of building decision tree models.On this basis,the classification model of decision tree is constructed through the given rule set,the specific process of model construction and application is formulated,and the accuracy of the evaluation model is verified by an engineering example.(4)By applying the research results of this paper to the specific process of protection of Bao ’en Temple in the construction of the right line of shield tunnel,the dynamic environmental risk assessment process of shield construction based on engineering data and the response guidelines of corresponding risks are elaborated,and the dynamic risk forecasting and risk counter measure of Bao ’en Temple in the construction of the right line are formulated.