Research On Environmental Vibrations Characteristics And Control Caused By Elevated High-speed Railway In Soil-rock Mixed Strata

Train-induced ground vibration is an increasingly serious problem,which has attracted enormous attention to the environmental protection.However,China is still faced with a variety of conundrums,i.e.,the environmental vibration standard system is lacking,the evaluation system is not coordinated with the engineering practice,and the prediction method research is limited by many uncertain factors,leading to that the residents make more and more complaints about the vibration and noise after almost all the new lines have been put into operation,which seriously affect the harmonious and rapid development of the rail transit.In this dissertation,dominant frequency bands of environmental vibration,prediction approach of the wheel-track high frequency vibration,ground vibration characteristics and control of high speed railway in hard rock strata are studied systematically.The major research contents include:1.Field experiment of vibration induced by elevated high-speed railway in the rock areaBased on the field test conducted on the Rizhao-Lankao high-speed railway of the typical bedrock shallow stratum,time domain peak,spectrum curve,and the constant-Q non stationary Gabor transform were imposed to analyze the bridge vibration and ground vibration characteristics,and the transmission rule of the vibration wave in the bridge structure,pile-soil system,and rock medium was studied.Furthermore,by comparing the basic calculation formulas of railway vibration source strength and model prediction method listed in ‘Guiding Suggestions on the Noise Vibration Source Strength Value and Governance Principles in the Environmental Impact Assessment of Railway Construction Project’,application conditions and rationality of the predicted parameters were talked about,and propositional geological correction parameters under the hard rock conditions were provided.2.Selection method of the effective frequency band for wheel-rail excitationConfirming the frequency band concerned by the current environmental vibration and noise through literature review,and taking the CRTS Ⅲ slab track of the typical elevated railway and the simple supported box girder bridge as research objects,slab track-viaduct structure frequency domain analysis model was established,and dynamic response amplitudes and frequency characteristics of different structure units were studied under1～1500Hz broadband harmonic load.On this basis,in order to explore the correlation between input excitation and output response,the transfer ratio between two points was defined,the concept of cumulative transfer ratio was introduced,and an approach was proposed to select the effective frequency range of wheel-rail excitement for the cumulative probability function model.3.Analysis model for the vehicle-track-bridge-pile-rock systemBased on the multi-body dynamics theory,and finite element and modal superposition method,this study proposed a computational method for vibration source of high-speed railway considering both the wheelset and the track flexibility.In this way,the limitation of over-simplification of train load in the traditional environmental vibration prediction was broken through,the existing analysis range of excitation frequency was extended,the simulation of structural vibration action under the short-wave irregularity excitation at wheel-rail interface was achieved,a pile foundation-rock and soil mass coupling vibration analysis model was constructed,and the frequency response characteristics of the system under different field conditions were studied.Based on this premise,a coupling analysis method was gained,which minutely considered the full path of broadband train load transmitted from the track,the detail components of the bridge,to the bridge pier,the pile foundation,and the rock and soil mass.In addition,a numerical prediction model of environmental vibration induced by elevated high-speed railway was established.4.Study on the influence of wheel-rail damage on vibration source characteristics of high-speed railwayOn the basis of the train-track-bridge rigid-flexible coupling dynamic analysis model,three general types of high frequency excitation source characteristics in the wheel-rail system induced by the wheel-rail damage were studied in particular,including short-wave irregularity on the rail surface of weld,rail corrugation,and low-order multiple deformations of wheels,and the influence on the dynamic response of vibration source strength of elevated high-speed railway was analyzed in detail.Moreover,the influences of track irregularity,train speed,weld amplitude,and polygonal wheel order were also analyzed,and the vibration source caused by railway were described more comprehensively.5.Study on environmental vibration and control caused by the high-speed railway in hard rocks strataAccording to the stratigraphic conditions of field measured fracture surfaces,based on the direct stiffness method of transfer matrix,the motion equation of elastic waves in the isotropic stratified rock medium was solved,the vibration transmission characteristic of soil-rock binary stratigraphic system was explored,and the characteristic frequencies found from the experimental results were verified.In addition,on the basis of the coupling vibration analysis model of pile foundation-rock and soil mass,the ground vibration characteristic induced by wheel-rail broadband excitation and the influence of typical stratigraphic structural parameters were further studied,effectiveness of the open trench and the wave resistance block for vibration isolation were analyzed in comparison,and a control method was proposed for environmental vibration on the hard rock strata.