The Safety Risk Assessment Of Tunnel Construction During Crossing The Metro And Zhe Study Of Zhe Core Congtrol Technic

With development of society and economy,China transport construction develops rapidly in recent years and will boom for a long period.During the course of construction,severe accidents frequently happened in past years because of some subjective or objiective reasons which shocked all people.It is urgently required that risk management should be applied to the entire process of tunnel construction,in order to ensure workers,machinery and property are safe enough.It is no doubt that risk management will be popular and absolutely necessary in tunnel engineering.Based on broadly surveying the risk management documents at home and abroad, and making full use of successful engineering risk management experience of the new tunnel passing from the bottom of the existing subway in the past,By summing up and refining,risk evaluation and management has been set up,related key technologies being bettered.And the research results have been introduced to Beijing Metro 5 passing over exsited Metro 2,which have gained remarkable safty and profit fruits.(1) Building up a basic scientific research system for tunnel project,given connotative meaning of project risk management system when new tunnel passes over existing subway,given the basic process chart with the dynamic risk-based analysis of the new tunnel passing the existing subway.Cleared ideas and scope of study the new line passes from the bottom of the existing subway.Several key issues were brought forward about the basic theoretical study and risk control in tunnel engineering risk administration.(2) Summed up the reasons of arising risk security and their risk factors the new tunnel passes from the existing subway with the shallow mining tunnel method. Detailed analyzed the status assessment process of the existing line and the security risk rating before the new tunnel passing from the existing subway.The existing structure's evaluation level Determining be determined by setting the scope and content of assessment.The levels evaluation can be determined to specific projects;the paper also refers to the contents and methods of the investigation and detection to the existing line(3) Analysis method that bases on monitoring data being on the basis of the theory of dynamic risk is the most appropriate method subtitling for risk assessment and management in tunnel construction,it is consistent with the tunnel project "dynamic design,construction dynamic" characteristics.The method comes into being by the actual site inspection records,according to monitoring data and the characteristics of the tunnel project,and surveying the dynamic risk factors,therefore it is more targeted than the conventional risk analysis method.It can greatly reflect real terms that risk dynamic changes with the tunnel construction process,and take an effective risk management and control in tunnel construction projects.(4) The application show that of dynamic risk analysis method based on monitoring data and risk assessment can dominantly reduce risk in the tunnel passing over existing metro.Especilly,construction management,grouting construction,strata lifting with grouting method,tunnel supporting,lining construction and tunnel excavating has changed in the process of dynamic control,such as level of risk has reduced from the original fifth or fourth to fourth or third.The above shows that the dynamic risk tracking and control can effectively reduce the construction risk when the tunnel passes from the existing line,which has obvious benefits to the risk prevention.(5) Summed up the current risk assessment system to be followed the principle in home and abroad,indicated the relationship between broad and narrow risk assessment's index.The meaning of the risk control in tunnel construction is improved. Summed up tunnel risk control indexes and control values.According to the existing line and its importance to society after a risk of causing economic losses and social implications should follow the idea the technical control is main,non-technical as a supplement.(6) I gained several key technologies of the risk control in the tunnel passing from the existing line,the achievements show below:1) Based on former study,the key problem:interaction and control target: engineering safety for new subway passing from the bottom of the existing line is studied.According to different aims in different construction stages,5 main technical points are summarized and technical system for such passing project is formed.In this thesis studies are carried out respectively for each different technical points.2) The magnitude of displacement in each construction step is analyzed using energy method.Settlement control standards of each construction step for the existing line is made.According to the characters of the new line and operation requirements for the existing line,monitoring measures are formed.These analyses and feed back measures are made to ensure the safety of existing structure.3) Grouting used in subway for existing line lifting up is studied.The research of grouting parameter and grouting method can offer guidance to this kind of project.(7) Trying to build an alarming and rescue system when tunnel passing over the existing metro.Effective analysis,feedback and alarming system has been organized and drilled successfully.Through researching and analyzing the impact to existing line and prediction analysis,monitoring systems have been studied and chosen to enable it to real-time control the state of the subway structure and the track system.Formulated the corresponding deformation control measures and emergency measures,according to the monitoring feedback and analysis,and take timely measures or adjust the construction scheme to ensure the operational safety,And,I make a more detailed refinement on the basis of the current three-level management of the rail tunnel,which is convenient to operate and practise.