Safety Control Research On Ultra-shallow Bored Tunnel With Large Pipe Shed Undercrossing Metro Subgrade

With the continuous development of the urban metro network,a large number of crossing metro projects emerge inevitably in range of the metro control protection. Metro lines are different from general building, whose allowable deformation control value are very strict, usually in millimeters. Ultra-shallow bored tunnel with large pipe shed undercrossing metro subgrade will disturb inevitably the metro lower soil layers which lead to metro line generating transverse and vertical deformation. Larger deformation would cause additional track irregularities which results in less safety to passengers and operation of the metro train.The safety control research on ultra-shallow bored tunnel with large pipe shed undercrossing metro subgrade has important theoretical significance and practical value for metro operation safe as well as similar construction.In this paper, safety control research on ultra-shallow bored tunnel with large pipe shed undercrossing metro subgrade has been researched comprehensively and systematicly, includeing ANSYS numerical simulation analysis, comparative analysis of field monitoring data and numerical simulation, SIMPACK multibody dynamics analysis and risk control measures.The main works and achievements are listed as below:.1.Comprehensively sum up risk control about ultra-shallow bored tunnel with large pipe shed undercrossing metro subgrade related information. Summarize key problems of shallow depth bored tunnel crossing metro subgrade project, including risk analysis about shallow depth bored tunnel crossing construction, pipe shed support effect, the metro car dynamic effects due to track deformation.2.Establish three-dimensional finite element model to analyze the metro structure deformation:Based on the practical engineering, analyze the deformation laws of both the metro structure and track railway. The results show that:Track deformation shows a U-shape settlement trough, its width is about3times of tunnel span; the track deformation caused by-1.5to3times tunnel span, rail deformation rate came faster and deformation account for more than60%of the total deformation; Support effect of differern pre-reinforcement measure can be expressed as:no support<small pipe support <pipe shed support<pipe shed and pipe shed support.3.Analyze the actual measured data and numerical simulation results based on practical engineering. Compare the actual measured data and numerical simulation results, proof the reliability of numerical simulation from station deformation and track deformation. In addition,analyze the causes of errors.4.Establish vehicle-trackSpatial coupling dynamic model to analyze vehicle dynamic performance:analyze vehicle dynamic performance based on derailment coefficient and the vehicle vibration acceleration before and after undercrossing construction. The results show that derailment coefficient and the vehicle vibration acceleration both increase significantly, the deformation caused by crossing project affect the security and comfort of metro.S.Put forward the risk control measures about shallow bored tunnel undercrossing metro subgrade:Aimed at shallow bored tunnel undercrossing metro subgrade, put forward the risk control measures from four aspects including risk assessment analysis, tunnel surrounding rock reinforcement, metro subgrade protection control and risk monitoring.