| Crossing construction has become one of the major risk sources for the safe operation of the existing Metro lines.The basic task to ensure the normal operation of Metro lines and the implementation of new engineering,is to discuss the safety of the existing Metro,from the perspective of risk assessment and control.At present,the analysis and modeling of risk assessment indicators has become one focus of the research,due to the particularity of the existing Metro lines,the personnel characteristics of different participating parties,management measures and so many other factors.Secondly,it will also affect the result of risk management and control of the crossing construction and the existing Metro lines,if the assessment only focuses on analyzing the risk source and studying specific engineering control technologies,while ignoring the analysis from the perspective of risk bearing body system.With statistical case studies of the crossing construction in Beijing,identification of risk factors affecting the safety of the existing Metro is carried out.The complex crossing system is divided into subsystems of new construction subsystem,geological environment subsystem and the existing Metro subsystem.Then,vulnerability assessment index system is set up based on the research of definition and characteristics of vulnerability,and vulnerability risk assessment method of the existing Metro is put forward.Finally,risk dynamic control system is established for the existing Metro.It mainly includes the following aspects:(1)Based on the statistical analysis of typical cases of crossing construction cases in Beijing,the accident characteristics and influencing factors of existing Metro lines are obtained.Defining of the accident of crossing construction,risk factors is identified in four dimensions,which are new construction excavation area,construction methods,distance from the existing Metro,etc.(2)The relationship between vulnerability assessment and risk assessment is established.It is pointed out risk is the result of disturbance act on the vulnerable system.Vulnerability of the existing Metro is clarified.According to vulnerability sequence evolution,3 elements of vulnerability characteristics are put forward,named the degree of exposure,sensitivity and fitness.The index system of vulnerability assessment is constructed,which includes the new construction,managemental and personnel factors,etc.(3)Based on the basic principle of the catastrophe progression method,the vulnerability assessment model for the existing Metro lines is established,and the threelevel assessment index system is determined.According to the calculated vulnerability index,the vulnerability of the system was divided into four grades.A risk assessment method based on vulnerability is established based on risk loss level and passenger volume of existing Metro lines.(4)Based on the Hall 3D structural model,a risk control 3D model for existing Metro lines is established with the axes of "constructing process dimension","participant responsibility dimension" and "risk controlling process dimension".With this model,the risk dynamic control method is put out.The key points of design for the crossing construction were summarized,and the case database was established based on CBR principle,so the new designs can be carried out based on cases of the database.The vulnerability assessment index system of the design is given,and then the quantitative assessment of different designs can be realized,providing a basis for the decision of complex projects.By combining the BIM model with the finite element software,the integrated analysis of the impact of new construction on the existing Metro is achieved,and the phased dynamic control indexes of different constructing steps are obtained,which help to establish a risk dynamic control system.In addition,BIM and Bentley collaborative platform are used as basic tools to build an information management platform framework for risk management and control for the existing Metro lines.(5)In order to relieve the difficulties of the existing Metro managers from managing the crossing construction projects,the hierarchical management system was proposed,and the specific control measures according to different risk levels were discussed.(6)Based on a new case of a bridge overcrossing the existing Metro tunnel,vulnerable analysis is carried out for the two schemes.According to the calculation result,Counterweight Jacking Method for the case is put forward.By integrating the BIM model and finite element analysis,formulating the controlling indicators of the existing Metro line and control measures of deformation in different stages,the floating deformation of the Metro tunnel is less than 1 mm when the project completed. |
