Research On Safety Risk Management Of Deep Foundation Pit Construction ——Take The 11# Plot Project In The Core Area Of Tongzhou Canal In Beijing As An Example

With the rapid development of China’s economy and the acceleration of urbanization,new urban buildings are developing towards the trend of deeper underground and higher above the ground.There are more deep foundation pit projects,and the excavation depth continues to refresh the engineering record.However,it also increases the risk of damage to the surrounding existing buildings,pipelines and roads,resulting in safety accidents endangering the vital interests of the people,such as the collapse of roads,surrounding buildings and foundation pit collapse.Therefore,it is timely and necessary to study the safety risk control of deep foundation pit construction.Firstly,based on the review of the research results of safety risk assessment of deep foundation pit construction at home and abroad,this paper determines the research direction,and puts forward the central problem of how to evaluate the safety risk of deep foundation pit construction in Beijing Tongzhou Fuli center project 11# plot.Secondly,WBS-RBS risk coupling matrix model is used to identify the safety risk of deep foundation pit construction in 11# plot.Through matrix coupling and combined with the opinions of project experts,72 main risk points are obtained.These 72 risk points are further screened and combined to obtain 40 risk sources,and a list of risk sources is prepared.The three-level risk evaluation index of each level of foundation pit is constructed by using the method of c-11# hierarchy,and then the risk evaluation index of each level of foundation pit is calculated by using the method of c-11# hierarchy;The assignment method is used to construct the corresponding membership function model to evaluate the safety risk of deep foundation pit construction in 11# plot.It is concluded that the risk level of concrete support construction（W3）and reserved soil platform composite soil nailing wall support construction（W6）is grade II,and the risk level of earth excavation and drainage construction（W7）is grade III.Conclusion that the risk level of anchor cable cutting and soil reinforcement construction（W1）,diaphragm wall construction（W2）,prestressed anchor cable construction（W4）and reverse structure construction（W5）near the subway is level 4 and the overall risk level of construction is level 3.Finally,according to the results of risk assessment,in the safety risk control of deep foundation pit construction,we should focus on the risk control of anchor cable cutting and soil reinforcement construction（W1）,diaphragm wall construction（W2）,prestressed anchor cable construction（W4）and reverse structure construction（W5）,and prepare special construction measures and foundation pit emergency plan.Deep foundation pit engineering is a project with great risk,and its risk management has certain practical significance.The methods of risk assessment and the examples of risk management and control of deep foundation pit engineering close to the subway side in this paper can provide reference for managers of deep foundation pit engineering to understand,analyze and deal with the safety risks of deep foundation pit construction.