Experimental And Numerical Research On The Vibration Isolation Performance Of Tunable Surface Wave Barrier

It is an effective method to set periodic barriers on the propagation path to cut off the vibration effectively.However,traditional single-form barriers often have a vibration isolation effect just in a specific frequency range.So it is of great practical significance to design a barrier that can isolate vibrations in different frequency ranges by changing the configuration.Based on the theory of periodic structure,this paper designs a tunable surface wave barrier for the main frequency of environmental vibration of 20-80 Hz.The tunable barrier has three adjustment methods to adapt to changes in the main frequency of vibration caused by environmental vibration.In this paper,the numerical simulation and experimental research of the 1:20 small-scale model of the tunable barrier are carried out respectively.The dispersion curve under each adjustment mode is calculated,the formation mechanism of the band gap is analyzed,and the change rule of the band gap with the adjustment mode is summarized.The numerical simulation results are compared with the attenuation domains under 12 operating conditions of the corresponding model experiments,and the reasons for the differences between the two are analyzed.Through numerical simulation,the anti-vibration isolation effect of the tunable barrier under different environmental vibrations is predicted.Combined with the experiment and engineering practice,the improvement opinions of the adjustable barrier are given.The corresponding conclusions are as follows:（1）Each tunable condition of the adjustable barrier has band gap characteristics.The arrangement of the finite period wave barrier has an obvious attenuation domain within the corresponding band gap.（2）Increasing the number of additional masses,the center frequency of the attenuation domain moves to low frequency;increasing the buried depth,the center frequency of the attenuation domain moves to high frequency;increasing the moving down distance of the upper block,the center frequency of the attenuation domain moves to high frequency.In the experiment,the amplitude of the attenuation domain of mass adjustment is the largest.These attenuation domain change have good agreement in experiments and numerical values.（3）In the numerical simulation and experiment,the attenuation domains with mass gradient and buried depth gradient arrangement is wider than that with periodic arrangement.（4）A loose soil layer is built around the model column.As the thickness and the looseness of the soil layer increase,the attenuation domain moves towards low frequencies as a whole,which is consistent with the phenomenon that the attenuation domain is generally lower than the numerical value in the experiment.（5）When the train speed drops from 350km/h to 250km/h,if the barrier is not adjusted,its vibration isolation effect may disappear,and it may even amplify the vibration.After adopting adjustment methods such as increasing control components and reducing the buried depth of the barrier,it can reduce and isolate the environmental vibration generated by the train at a speed of 250km/h.（6）Pre-burying a hollow sleeve in the soil can reduce the interference to the surrounding soil when adjusting the barrier.After adding the sleeve,increasing the buried depth can still increase the attenuation range and generate new attenuation at low frequency area.