Vibration Isolation Performance Of Periodic Piles Under Moving Loads

In recent years,with the rapid development of rail transit construction,how to reduce the environmental vibration and noise caused by train operation has become an important research topic.Among them,the vibration isolation system with periodic row piles has become a research hotspot due to its unique attenuation domain characteristics.However,due to the moving load of rail train,the research on attenuation effect of periodic row piles on soil response caused by its moving process is not perfect.Therefore,starting from the propagation path of vibration,this paper takes the elastic soil as the research object,adopts the basic methods of three-dimensional finite element and numerical simulation,combined with the characteristics of periodic structure attenuation domain to analyze the soil response under the action of train moving load and the attenuation effect of soil response after using row pile isolation system,and comprehensively evaluates the vibration isolation effect of row pile.The specific work is as follows:Firstly,a three-dimensional finite element model of harmonic moving load soil periodic row pile is established.The displacement time history response of each monitoring point on the surface of elastic soil under harmonic moving load is analyzed,and the change trend and law of the response of each monitoring point are obtained.The influence of moving load speed,row number of piles,row depth and period constant on the vibration isolation effect is mainly discussed in this paper.The results show that the vibration isolation effect of row piles increases with the decrease of moving load speed;It increases with the increase of the number of piles and the depth of piles;It increases with the increase of the period constant of the typical element.Secondly,according to the characteristics of moving load,the effective vibration isolation range is studied.The variation of the effective vibration isolation range of row piles with the moving load and the relative position of row piles is studied,and the influence of different row pile number on the vibration isolation performance and isolation area of row piles is analyzed.Then,by changing the action frequency of harmonic load,the frequency response function of vibration isolation of single row pile under harmonic moving load is calculated and compared with the attenuation domain of periodic row pile,it is found that the attenuation effect of input load whose load frequency is in the attenuation domain of row pile structure is obviously stronger than that of other frequency loads.Finally,based on the actual train load,the vibration isolation performance of periodic piles is studied.Considering the problem of response superposition caused by multi axial load of rail and train,the track soil coupling model is established to calculate the displacement response law of elastic soil and the vibration isolation effect of periodic row piles under the combined action of wheelset load of two carriages of ordinary train and heavy haul train.The influence of vehicle speed and the number of piles on the vibration isolation effect is mainly discussed.The results show that the periodic row pile structure has a good vibration isolation effect on the moving train load,and its vibration isolation effect decreases with the increase of train load speed and increases with the increase of row pile number,but the type of train has little effect on the vibration isolation effect.Through the exploration of this paper,it provides a certain design basis for the practical application of periodic pile structure to reduce the environmental vibration caused by train load.