Study On Soil Vibration Induced By Subway Train And Effect Of Damping Track

Nowadays,subway has occupied the vast majority of the operating mileage of urban rail transit in China.It has the advantages of large volume of traffic,low pollution,no occupation of urban land resources and no impact from ground traffic jams and bad weather.So that it has become the preferred mode of transportation for urban People’s Daily travel.However,the environmental vibration caused by subway operation will affect People’s Daily life.In this paper,based on the background of Xi ’an metro engineering,the environmental vibration model of foundation,tunnel and soil under the rail was established.Besides,the propagation law of vibration caused by subway operation in soil was studied,as well as the influencing factors of vibration reduction effect of different vibration reduction tracks.The main works are as follows:(1)A wheel-rail coupling model was established.And the time-history curves of the support reaction force of the fastener at different speeds were obtained through numerical calculation.The support reaction force load of the fastener was applied to the foundation-tunnel-soil finite element model under the rail for soil vibration analysis.(2)Vibration propagation in soil under different train speeds,tunnel depth and soil dynamic characteristics is studied: When the vehicle speed increases,the vibration will be enhanced.But when the vehicle speed exceeds a certain critical value,the vibration will be weakened.The farther the ground point is from the vibration source,the smaller the critical value will be.The further the distance is,the smaller the amplitude of vibration acceleration increases with the increase of velocity.Besides,the speed has no effect on the location of vibration amplification region;The greater the buried depth of the tunnel,the weaker the vibration response.The farther the distance,the lower the amplitude of vibration response weakening.The location of the vibration amplification area is related to the buried depth,and its peak value is roughly equivalent to the buried depth.With the increase of the buried depth of the tunnel,the number of vibration amplification area will also increase;With the increase of dynamic elastic modulus of soil,the ground vibration will be weakened.And the descending trend of acceleration vibration level first increases and then slows down.The larger the dynamic elastic modulus is,the closer the vibration amplification area is to the vibration source,and the number of vibration amplification area will increase.(3)For the mixed fill soil,new loess,medium sand and silty clay layers,the frequency range of vibration amplification caused by vibration propagation in different soil layers is analyzed respectively: The larger the dynamic elastic modulus of the soil layer is,the larger the frequency band range of the vibration amplification zone will be.However,the vibration amplification zone is always caused by the low frequency band vibration of 3.15-16 Hz.It should be paid attention to avoid the resonance caused by the natural vibration frequency of the building approaching this frequency band range.(4)For steel spring floating slab and vibration damping pads the damping effect of floating slab track values in time domain,frequency domain was analyzed.And evaluate whether the vibration reduction effect at each tunnel wall meets the specification requirements.The influence law of train speed and tunnel depth on vibration reduction effect of vibration reduction track is studied.Besides,the value of train speed and tunnel depth when vibration reduction effect is best is obtained.