Prediction Study On Ground Microvibrations Caused By Elevated Urban Rail Transit

In recent years,urban rail transit has been developing vigorously in China due to its advantages of high traffic volume,high-level safety,punctual operation and no traffic jam.Elevated rail transit is an important line form in urban rail transit due to its short construction period,convenient maintenance and flexible line arrangement.Urban rail transit,while relieving urban traffic pressure,also causes vibration pollution to life,production and scientific research areas along the route.In order to reduce the rail vibration pollution influence on precision instrument production equipment near line,it is necessary to predict environmental vibration caused by rail transport,for taking effective vibration reduction measures of the urban rail transit planning and design.Based on the engineering background of the vibration impact caused by Xiamen rail transit line 4 to the M3 plant of Xiamen Tianma microelectronic Company,the prediction study of the ground micro-vibration induced by urban elevated rail transit vehicles is carried out.The main research contents and results are as follows:(1)This paper researches the development of urban rail transit in China,according to related literature both at home and abroad,summarizes the research status of environment vibration of urban rail transit,simply introduces the environment vibration evaluation index and control standards.(2)Combined with analytical method and finite element method(FEM),this paper establishes the model of vehicle-track-bridge vertical coupling vibration source,excited by the vertical combined track irregularity,calculates the dynamic wheel-track contact force and the support reaction of the concrete simply-supported beam bridge when the subway car B passing through the bridge at different speeds.(3)A field experiment is carried out to study the vibration transmission of the site soil between Xiamen rail transit line 4 and the microelectronic factory,which uses heavy truck drive and manual hammer drive and measured the propagation rule of ground vibration.Then the finite element(FE)model of bridge pier-pile-soil vibration propagation path is established,and the soil parameters in FE model is modified with the experimental results.(4)The bridge support reaction in the vibration source FE model is loaded on the top of piers in the vibration propagation path FE model as external drive,and the ground micro-vibration response under the train operation of elevated rail transit is calculated.Based on the calculation results,this paper analyzed the propagation attenuation law of ground vibration,and discussed the influence of the foundation soil property,foundation form and driving speed on ground vibration response.The calculation results can provide reference for the planning of urban rail transit and the vibration reduction design of sensitive sites.