Research On Safety Risk Management Of Adjacent Bridge Induced By Subway Shield Construction

In response to the problems of small urban space and traffic congestion caused by an expanding city and a growing urban population,the metro,with its advantages of effective use of urban underground space,avoiding traffic congestion,and having a large load-bearing capacity,has been developed,of which the shield method is widely used because of its fast construction speed and strong adaptability to the ground.As the metro is generally built under urban traffic roads,and various footbridges and overpasses have been constructed in the area,it is unavoidable that the metro shield construction needs to cross the side or underneath the pile foundations of the adjacent bridges,and due to the soil parameters and complex external environment of the metro shield construction,the surrounding strata are bound to settle to varying degrees due to the shield construction,thus transferring the resulting deformation and displacement to the pile foundations of the adjacent bridges.The pile foundations of the adjacent bridges will be subject to settlement and additional stresses,which will change the pile-bearing capacity and affect the superstructure loads,thus posing a risk to the adjacent bridges’ normal use and structural safety.Therefore,a safety risk evaluation index system is constructed to evaluate the safety risk of the adjacent bridges induced by the construction of the shield structure of the metro,and on this basis,a safety risk evaluation model for the adjacent bridges during the construction of the shield structure is established,and corresponding risk countermeasures are proposed based on the evaluation results to ensure the safety of the construction of the shield structure of the metro and the structural and operational safety of the adjacent bridges.Based on the existing research,this paper conducts a study on the safety risk management of adjacent bridges induced by metro shield construction in Lanzhou Metro Line1,Phase I Project,Section II,which mainly includes the following aspects:Firstly,a large number of relevant literature specifications and Citespace article searches are analyzed in depth,and the causes of risk events and their evolution are analyzed layer by layer through the fault tree method in conjunction with accident causation theory,based on which the safety risk occurrence mechanism is analyzed and its model is established,and the safety risk factors that affect the adjacent bridge structure during the construction of the metro shield are analyzed and identified comprehensively to establish The list of safety risk factors induced by metro shield construction on adjacent bridges is established.Secondly,a decision table for the safety risks of the adjacent bridges is constructed and a cloud model is used to discretize the continuous attributes to achieve a simplification based on information entropy,which is a common algorithm for attribute simplification based on a rough set theory,to remove the risk indicators that are weakly correlated or have similar meanings to obtain the final evaluation index of the safety risks induced by the construction of the metro shield on the adjacent bridges.Again,the evaluation index system of the safety risk induced by metro shield construction on adjacent bridges was established,and the combination of grey group clustering(GGC)and improved criteria importance through inter-criteria correlation(ICRITIC)was used to assign the risk indicators.Due to the existence of a large number of random uncertainties in the construction process of the metro shield,the evaluation results have certain deviations.Therefore,to address the problems of imperfect and distorted safety risk assessment results of the adjacent bridges induced by the construction of the metro shield,a metro shield construction-induced safety risk assessment model based on the variable-weight top clinic model is constructed.Finally,based on the actual project situation of Lanzhou City Urban Rail Transit Line 1Phase I Project Section II,the safety risk evaluation of the adjacent bridges during the construction of the metro shield tunnel is analyzed,and the safety risk level of the bridges adjacent to the metro shield tunnel line and the key risk factors that lead to the occurrence of safety hazards in this section is obtained,and corresponding preventive and countermeasures are formulated accordingly for This will provide a scientific and effective reference for the prevention and control of safety risks induced by metro shield construction on adjacent bridges,and help improve the safety of metro shield construction and reduce the impact of disturbance on adjacent bridges.