Safety Risk Assessment Of Subway Construction Based On Shield Method

In the rapid development stage of subway construction,shield tunneling method is widely used because of its advantages such as little pollution,high degree of mechanization,high efficiency and little environmental impact.However,due to the uncertainty and complexity of the construction environment,there will be a lot of safety risks and even accidents in the process of shield construction.Therefore,it is necessary to conduct research on safety risk assessment of shield tunneling construction to eliminate hidden dangers and control construction accidents.The main research contents of this paper are as follows:(1)Firstly,based on the risk assessment of subway tunnel shield construction at home and abroad,introduced the theoretical knowledge related to risk assessment management,and studied the risk identification,risk estimation and risk assessment methods respectively according to the basic process of risk assessment management.(2)Secondly,according to the characteristics of tunnel shield construction,using the work breakdown structure method,work breakdown shall be carried out in ten aspects:end reinforcement,working well construction,preparation before departure,shield departure,shield tunneling,preparation before shield reception,shield arrival,shield reception,construction of connecting passage,crossing special terrain,shutdown and overhaul and change the knifed.According to the accident probability table of the LEC method and the risk classification table of the pre-risk analysis method,according to the shield construction process,the risk factor analysis is carried out,and the risk factor,risk level,risk result and risk control measures are preliminarily analyzed.(3)Again,the evaluation method of this paper is selected,the reasons for selection are discussed,this paper determines the pre-risk analysis method,analytic hierarchy process(ahp),application of expert investigation method combined with on-site inspection.According to shield construction,from the perspective of pre-risk analysis,this paper analyzes definition,application steps,principles and classification,and introduces the process and application steps of ahp,as well as the objects and contents of on-site testing.(4)Finally,based on the example of shield tunnel project from Xingfu Town station to Nantong railway station of Nantong Rail Transit Line 2,it carries out the risk identification analysis and the measure formulation,design the questionnaire of expert scoring,combined with on-site inspection,determine the weight,assess the risk factors.it is concluded that should focus on prevention connecting passage construction,shield tunneling,through building risk,mainly for ground settlement risk,structural damage,segment breakage leakage risk,gushing water sand,needs to be monitored in a timely manner to ensure that monitoring in place,strengthen the synchronous grouting,ensure that the secondary grouting quantity,optimization of construction parameters,control the grouting problem of melting and sinking well,to improve the safety of the follow-up shield construction.There are 23 pictures,61 tables and 72 references in this paper...