Cause Analysis And Control Research On Ultra-limit Of Deformation Of The Existing Tunnel Undercrossed By Shield Tunnel

With the increasingly intensive distribution of urban subway network, urban municipal engineering is very likely to be affected and intervened by new construction project, such as civil or industrial construction of foundation pit engineering, crossing engineering of underground municipal utilities of heat, electricity, water, drainage and cable, and crossing engineering of traffic facilities of roads, bridges and new rail lines, etc.. Taking Beijing as an example, in recent years during the construction of urban municipal engineering, it is inevitable to face the problem of crossing some existing rail transit line. All these problems are directly connected with both the structure and track of the already existing rail transit, and the normal operations of the existing lines, which pose a serious challenge to the rapid construction and development of urban rail transit. Therefore, they must be properly dealt with.The project of Beijing subway shield undercrossing the existing subway is taken as the research object, The tasks fulfilled in the dissertation are1isted below:(1) Through consulting a large number of related documents at home and abroad, systematic deep summarizes the core content of shield tunnel crossing construction which includes settlement prediction and influencing factor of shield crossing construction from theory and technology.(2) Taking a specificshield tunnel project underneath passing the existing double lines of interval deformation and transfinite as an example, the author analyzes the deformation of the existing shield tunnel, summarizes the deformation laws.(3) Based on the real construction parameters, the author uses ANSYS software to establish3-dimentional entity model in which stimulates how the shield tunnel construction affects the existing double lines shield tunnel. Meantime, under the condition of normal operations of the existing subway, analyzing how shield tunnel excavation influences the deformation of the existing track structure.Compared with the monitoring data, the reliability of the calculation model is to be verified.(4) By analyzing the construction parameters of shield tunneling and simulation results, Summarizing the reasons of transfinite deformation caused by subway shield undercrossing.(5) The last part is to summarize the safety control measures of deformation and transfinite when shield crosses the existing lines, which aims to give advice on typical crossing engineering in terms of safety control measures.