Trenches For Reduction Of Train-induced Vibrations On Adjacent Buildings By 2.5D Finite/infinite Element Approach

In recent years,more and more subways and high speed railways have been built to alleviate traffic congestion in major cities.The problem of vibration and noise induced by moving train has attracted the increasing attention from researchers and engineers.By the 2.5D finite/infinite element approach,Yang and Hung in 2001 studied the 3D wave propagation behavior of the train-soil-structure system.In this paper,the steady-state dynamic response of half-space due to the moving train is discussed,and the accuracy of the 2.5D result is verified by comparing with the theoretical solution.Assuming the material and geometric properties of the soilstructure system to be identical along the railway direction,a 2.5D analysis is presented of the vibration isolation of buildings alongside the railway by open or infilled trenches.In addition to the train and trench correlation parameters,the influence of the track roughness has also been incorporated.The major conclusions are drawn from the results obtained:(1)The 2D responses of the building are all higher than the 2.5D responses for trains moving at normal speeds,as the vibrational energies of the 2D model cannot be dissipated along the railway direction.(2)The frequency response function(FRF)for the model with building is less than that without building,while they get closer in the low frequency range(< 10 Hz)for increasing train speeds.Ignoring the soil-building coupling are generally on the conservative side.(3)Both open and in-filled trenches are good for reducing train-induced vibrations of buildings,especially for those with higher self-oscillation frequencies.But the open trench performs better than the in-filled trench for the case studied.(4)The fact that the 2.5D floor response is always higher than the ceiling response,contrary to the 2D analysis,means that the wave transmission effect along the railway direction due to the building-soil composition is higher than the building amplification effect on the 2D plane.(5)The effect of rail roughness that is crucial to the velocity and acceleration responses of the building to moving trains,has only a slight effect on the displacement response.All findings in this paper give suggestions for the design of trench used to isolate the train-induced vibrations.The major contributions of this paper are as follows:(1)Based on the frequency domain analysis method,the dynamic strain and dynamic stress response of half-space due to the moving train is obtained,and the theoretical validation of the 2.5D approach is performed.(2)By 2.5D finite/infinite element approach,the effect of trenches with different parameters on reducing the train-induced vibrations of building is analyzed.(3)In the 2.5D analysis of train-induced vibration of adjacent buildings,the effect of track irregularities is taken into account.