Study On Near-field Barrier Isolation And Ground Vibration Induced By Train Load In Frozen Field Using 2.5D Finite Element Method

With the rapid development of rail transit in China,the environmental vibration caused by train is becoming more and more serious,especially because of the widespread distribution of the frozen soil in China,the environmental vibration in the frozen soil area has aroused more and more attention.On the one hand,due to the temperature sensitivity of frozen soil,it needs to be considered about the nature of soil varies with temperature.In addition,the high speed train exceeding Rayleigh wave speed will cause more vibration,which will affect the stable moving of the train.On the other hand,the operation of the train w ill affect the lives of the surrounding residents and the normal operation of the precision instruments.Therefore,the study of train environment vibration and vibration isolation in frozen ground has become an urgent problem.The main contents of this paper are as follows:(1)Based on the theory and method of 2.5D finite element analysis,the wave propagation in frozen soil under train moving load is systematically studied.The theory and numerical simulation method of response analysis for 2.5 dimension al frozen soil roadbed under moving loads are established.Due to the invariance of the soil and orbit in the direction of train operation,the three-dimensional problem is simplified as a two-dimensional plane strain problem through the Fourier transform of the wave number,and then the soil is discrete d on the cross section,in which the soil adopts the eight node isoparametric element and the boundary is bounded by the infinite element boundary.The discrete process takes into account the variation of soil parameters with temperature,and then obtains the three-dimensional response of the frozen soil foundation at any point by inverse Fourier transform.(2)Analyze the damage laws of moving train loads to frozen soil in cold regions.Based on self-made 2.5D finite method program,t he simplified train multi axle load on the frozen soil foundation with different temperatures,considering the self excited frequency of the train,analyses the acceleration time history,frequency spectrum and attenuation of low speed and high speed trains at different temperatures.It is found that the vibration response amplitude of high-speed and low speed trains is not very different due to the existence of self excitation frequency.The main vibration of train is vertical vibration,and the frequency distribution of high speed train is wider and the high-frequency part is more distributed.Moreover,the local rebound phenomenon of attenuation curve is analyzed.(3)Vibration isolation analysis of train vibration on frozen gro und.Based on the propagation principle of elastic wave and the vibration isolation mechanism of vibration isolation barrier,the method of in-filled trench near field isolation is chosen in this paper.The depth,width,distance from track center,materia l and surrounding soil temperature of different train moving speed are analyzed.It is concluded that the vibration isolation effect of the high speed train is better,the increase of the depth and width of the in-filled trench will effectively improve the vibration isolation effect,and the closer the distance from the center of the track,the greater difference between the material and the properties of the surrounding soil will also improve the vibration isolation effect.