Analysis of Ground Vibrations Induced by Metro Vehicles in Small Radius Curved Sections
Based on the engineering background of the small radius curve section,the ground-surface vibrations characteristics induced by train are investigated by in-situ test.Time-history analysis,frequency spectrum analysis,Hilbert-Huang spectrum analysis,one-third octave band spectrum analysis are carried out for selected testing data.Moreover,a three-dimensional FE model of track-sleeper-ballast-tunnel-foundation is established by using ABAQUS software,to study the metro induced environmental vibrations.And the effects of the buried depth of tunnel,the operation velocity of metro on the ground vibrations are analyzed and discussed in detail.The results show that the peak value of horizontal vibration velocity is about 1.5～2.0 times of that of vertical vibration velocity.The dominant vibration frequency is in the range of 10～20Hz and 80～90Hz,and the high frequency part attenuates rapidly with the increase of the distance far from tunnel.Further,the horizontal vibration response induced by metro operating in the small radius curve section is greater than that in the case of straight tunnel,while the vibration response the vertical direction is diametrically opposite.In addition,the peak value of the nearby horizontal vibration velocity is generally linearly attenuated with the increase of the tunnel depth,and the influence of the buried depth of tunnel on the horizontal vibration velocity is greater than that of the vertical vibration.Further,the tunnel depth basically has no influence on the dominant frequency of the horizontal vibration.The relationship between the peak value of the horizontal vibration velocity and the train speed is roughly parabolic,and the peak value of the nearby vertical vibration velocity also increases with the increasing of the train speed,while the increase is less than that of the horizontal vibration.The speed of metro has a significant effect on the dominant frequency of environmental vibration,and the higher the speed is,the higher the dominant frequency is.
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