Research On Subgrade Vibration And Barrier Vibration Isolation Of Rail Transit In Seasonally Frozen Area

The ground-borne vibration effect of train traffic on the surrounding environment is becoming more and more prominent.For seasonally frozen ground,a frozen soil cover is formed in winter,which changes the wave velocity structure of the ground.Railwayinduced vibration propagates through the ground with a hard cover and a soft substratum.The characteristics of the wavefield are yet to be revealed,and the vibration isolation effect of in-filled barriers is still unclear.In this thesis,a method of combining the measured data and numerical simulation is used to study the vibration of the subgrade and the adjacent soil in the northeast cold region.The main work is as follows.Firstly,the definition of the sub-track soil impulse response function is proposed,and the calculation formula of ballast dynamic compliance is given,and the evolution law of permafrost cover layer is expressed by means of the relationship between the dynamic shear modulus of soil and negative temperature and the measured data of ground temperature in winter.A finite element model of a numerical impulse response function that lays the foundation for modeling the dynamic interaction of sleepers and ballast.Then,based on the site impulse response function,a time-domain analysis model of the coupled vibration of train-track-3D finite element site is established,and the iterative calculation process for solving the differential-integral equation system of the system is given.way to verify the reliability of the model.To simulate the ground vibration of the Daqing Longfeng Wetland section of the Binzhou Railway under various temperature conditions,-10°C,-15°C,and-25°C were selected,respectively,to represent the air temperature in the initial,middle and deep winter periods.Based on the numerical results,the intensity and frequency characteristics of the free ground acceleration,the distribution of the vertical dynamic additional stress in the subgrade,and the variation of the Mises stress with various air temperatures were discussed.Finally,an underground vibration isolation barrier model was added to the finite element model of the site impulse response function to simulate and analyze the vibration isolation effect of the barrier.The effect of deep and barrier materials on vibration isolation and vibration reduction.The proposed time-domain method does not need to establish two different models(one simplified spring damper and one complex FE,as in conventional methods)for the same ground.Therefore,the intrinsic mechanical logic is more rigorous than the traditional method.Because the wave field of soil is synthesized by a convolution of the IRF,the method requires a small space domain of FE and enjoys a high calculation efficiency.The results obtained in this thesis are expected to be useful for the traininduced vibration reduction design in seasonally frozen regions.