Study On Safety Risk Assessment And Control Of Deep Foundation Pit Construction Adjacent To Existing Subway

The construction of deep foundation pit should not only ensure the safety of its own deformation,but also should ensure the construction impact to the existing subway tunnels in a safe and reasonable range.Compared with other projects,the construction safety accidents of deep foundation pit tend to show the characteristics of mass injury,large area collapse,vicious circle of interaction between water and soil,great influence of surrounding environment and huge economic loss.At the same time,due to the existing subway tunnel is the city's underground artery,carrying a huge daily traffic,in the event of a security accident,rescue will be extremely difficult to carry out,which will cause a lot of casualties,economic losses and social impact.Therefore,it has important academic significance to systematically and comprehensively identify the influence factors of safety risks under the constructions,to accurately and dynamically assess safety risk,to scientifically and reasonably take technological measures to control risks,and to control the deformation of deep foundation pit itself and existing subway tunnel.This paper mainly systematically studies the safety risk control of construction based on the deep foundation pit project adjacent to the subway tunnel in a city located in the middle of China.The main aspects are as followed:(1)Research on Safety Risk Assessment Model for Deep Foundation Pit Construction adjacent to Existing Metro Tunnels.At first,this paper constructs a safety risk assessment index system for the construction of deep foundation pit adjacent to the existing subway tunnel on the basis of statistical analysis of the structural deformation from the perspective of the cause of the accident.Secondly,based on the comparison of the safety risk assessment methods and the actual needs of the project,the BP neural network is improved,and a safety risk assessment model for deep foundation pit construction adjacent to the existing subway tunnel based on BP wavelet neural network is established.Meanwhile,based on the improved BP neural network theory,the safetyevaluation procedure and evaluation grade of deep foundation pit construction adjacent to the existing subway tunnel are determined.Finally,through the large number of sample data obtained in a project,the improved evaluation model and the original model are trained and tested to demonstrate the reliability of the model,which laid a theoretical foundation for the evaluation of safety risk control system.(2)Research on Safety Risk Control Technology System for Deep Foundation Pit Construction adjacent to Existing Metro Tunnel.Based on the theory of finite difference model,and take the elasto-plastic constitutive mechanism of soil as the relevant judgment criterion,putting forward the research method of safety risk control technology for foundation pit construction on the basis of the whole process of construction simulation.By comparing different programs and analyzing of a variety of influencing factors,and establishing parametric analysis of the code with finite difference method,a number of quantitative rules were calculated by the qualitative analysis.A complete set of construction control measures were taken to guide the construction,which laid a theoretical foundation for the control measures of the safety risk control system for the construction of the deep foundation pit adjacent to the existing subway tunnel.(3)Research on Safety Risk Control System for Deep Foundation Pit Construction adjacent to Existing Metro Tunnel.Based on the established safety risk assessment model and safety risk control technology system,the BIM management platform data format transformation is achieved and Safety Risk Assessment Model for Deep Foundation Pit Construction of Existing Metro Tunnel is embedded after designing the overall framework of safety risk control system by introducing the BIM technology with data transmit mode and usage pattern of BIM integrated platform,and after the developing the safety risk control system with BIM Navisworks software.Finally a set of dynamic and visual “assessment-analysis – control” security risk control system is established.