Study On Mechanism Of Stratum Displacement And Bridge Damage In Construction Of Metro Under Complex Conditions

Urban rail transit construction as the city small space for construction,surfaceconstruction (structure) of buildings and underground pipeline is complex, and thesubway construction in rock and soil interior, so in construction,we inevitably disturbthe surrounding rock and soil,damage to the original equilibrium state,transform to anew equilibrium state.Tunnel excavation makes the surrounding rock unloading,freesurface causing convergence deformation,causing the ground deformation; at the sametime, the disturbance of construction will make formation water loss, soil consolidation,the entire formation of consolidation is settle. When this series of settlement develop toa certain extent,will affect the surface construction (structure) of buildings andunderground pipeline ’s safety and the normal use seriously.Therefore, stratumdeformation caused by subway construction under the complex condition is theimportant topic we paid attention to and researched all the time.The paper studied the metro construction in city, faced with the complexgeological conditions, complicated construction conditions of excavation tunnelconstruction method,complex construction project boundary conditions of thesurrounding construction (structures) of buildings and underground pipelines.Construction risk and difficulty increases, surface deformation mechanism and theimpact on the surrounding environment caused by construction is relatively complex,domestic and foreign research achievements in this field are also less.The main studiedfollowing aspects:Firstly, this paper summarizes and analyzes monitoring technicalspecification,control index types and the numerical results of crown and surfacesettlement caused by excavation construction, through the detailed examples statisticalanalysis for typical city,put forward to the reference suggestion to control indexnumerical determination apply to the actual project.Secondly, taking Guangzhou Metro Sha-Feng interval of small clear distanceoverlapped tunnel construction as engineering background, using3D Lagrangedifference calculation software of different excavation sequence,characteristics researchof small clear distance overlapped tunnel construction surrounding rock nonlinearmechanical response.Study on the superposition effects of four tunnels of different excavation steps to surface deformation, analysis the deformation and stress change lawof tunnel surrounding rock and lining structure,according to the research results putforward reasonable measures to reinforce surrounding rock, control the surfacedeformation and guide the construction site,the calculated results are compared withmonitoring results of actual project,research shows that,the agreement.Thirdly, study of damagement that Beijing Metro Garden Bridge Station hole pilemethod construction to the adjacent bridge piles (Garden Bridge),using numericalsimulation software to simulate the Garden Bridge Station subsurface excavationprocess,calculate the failure on adjacent bridge piles and surface settlement in variousstage,give the bridge damage standard.In the study, comparative analysis the theoretical research numerical simulationand field monitoring results,the results show that, research results and actualmeasurement results are basically consistent,it illustrates the research achievement isreasonable.This research gives advance forecast effect for subway engineeringconstruction,provides a theoretical basis and guidance decision,solutes the technicalproblems in construction,accumulates valuable experience for the similar engineering’sdesign and construction.