Design And Research Of Periodic Row Piles In Metro Vibration Isolation

Urban rail transit in China has been developing rapidly in recent years.Urban metro has been favored by large and medium-sized cities due to its large volume,safety,reliability,convenience and punctuality.The operation of urban metro,meanwhile,has also caused serious environmental problems.With the strengthening of people's environmental awareness,environmental vibration has attracted more and more attention.Therefore,it is of great social significance and engineering value to research environmental vibration and its control measures.This paper combines field test,theoretical analysis and numerical simulation to study the design of periodic row pile isolation based on phonon crystal band gap theory.The main research contents are:(1)Based on the theory of phonon crystal in solid physics,the periodic characteristics of periodic row piles are analyzed.COMSOL finite element software is used to build a coupling simulation model of solid-solid physics field of periodic row piles,the bandgap characteristics of periodic structure are studied,and then the periodic pile structure model suitable for metro vibration reduction is proposed.(2)Field tests on the environmental vibration problems of common track beds in a single-line single-hole shield tunnel of a certain line of the Beijing Subway are conducted,and the data of rail,track bed,tunnel wall and surface from the center line of the tunnel at 30 m are obtained.After analyzing the data,it is concluded that the main distribution range of vibration characteristic frequency in near-field soil layer of metro is 40~80Hz.(3)The influencing factors of periodic row pile of Bragg scattering type are analyzed,including: the filling ratio,periodic constant,density and elastic modulus of matrix material,density and elastic modulus of scatterer material.And the influencing factors of periodic row pile of locally resonant type such as periodic constant,thickness of wrapping layer,density and elastic modulus of wrapping layer material,core radius,density and elastic modulus of core material,and density and elastic modulus of scatterer material,are analyzed.Each influencing factor law is presented.Through comparing the main influencing factors are obtained.Then the comprehensive sequencing of the influencing factors is put forward by the orthogonal test and the analysis of the influencing factors.(4)The optimal parameters combination schemes for the designs of periodic row pile of Prague scattering type and locally resonant type are proposed respectively.The band gap ranges of 49~69Hz and 42.3~89.1Hz can be obtained separately in the ideal periodic row pile arrangement.(5)By analyzing the frequency response function of periodic row piles under the scheme parameters,it is verified that the design of the periodic row piles possesses good damping performance.To sum up,the periodic row pile structure has the bandgap characteristics of phonon crystal in solid physics.By adjusting the pile row structure and the parameters of physical material,the reasonable and complete solution can be designed,which can also be effective measures for path vibration reduction in urban rail transit.