The Application Of Steel Spring Floating Slab In Subway Vibration Reduction

With the rapid development of social economy,more and more population flows into urban.To make it easier for people to travel,our country pay close attention to urban rail transit;Metro is increasingly becoming the first option to overcome the difficulty of urban traffic congestion for the kinds of advantages it have,such as high efficiency,on time,security and comfortable.Meanwhile,the vibration of the surrounding environment induced by subway operation brings lots of new troubles to the daily life of the residents.There is plenty of evidence to show that part of the subway operation areas have produced a great effect on people's physical and psychological health,and also have impact on precision scientific experimental instruments.This proofs that the research on vibration and noise reduction have important sense.Steel spring floating slab track has many advantages,such as efficient use of the geometric space of a tunnel,convenience of maintenance and replacement,long service life,and this make it widely used in subway construction.In many papers on the study of steel spring floating slab track it simplifying the vehicle as a moving load,which not take the interaction between vehicle and track system and the tunnel.To further explore the vibration damping characteristics of steel spring floating slab track,in this paper based on collecting related papers civil and abroad,firstly tunnel model and steel spring slab track model is established respectively by using ANSYS finite element software and the modal analysis is carried out.present the influence law of changing parameters of the stiffness of the fastener,the density and the thickness of the floating slab,the stiffness and spacing of steel springs on the natural frequency of the floating slab track system.secondly,using UM multi-body dynamics software,by means of FEM flexible subsystem can bring vehicle-floating slab track-tunnel together,calculating vertical force of wheel and rail.Last,establishing steel spring floating slab track-tunnel-ground 3D model by ANSYS software and then applying the vertical force of wheel and rail to the rails,analysis the influence rule of changing parameters of the stiffness of the fastener,the density of the floating slab,the stiffness and spacing of steel springs on the vertical displacement and acceleration of floating slab and rails;using vibration acceleration level to analysis all parameter change how to influence surface vibration.The calculation results show that the density and thickness of floating slab,the stiffness and spacing of steel spring have great effects on the natural frequency of the floating slab track system,and it can be considered as a key consideration;the stiffness and damping of fastener,the density and thickness of floating slab,the stiffness and damping and spacing of steel spring have different effects on the vertical displacement and acceleration of the rail and the floating slab.Increasing the stiffness of fastener can decrease the displacement and acceleration of rails,the result in favor of reducing wheel rail wear,prolonging life of rails;increasing the stiffness or decreasing the spacing of spring,can reduce the degree of vibration of the system,the displacement and acceleration of the rails and the floating slab;enlarge the damping of fastener and floating slab and the density of floating slab can make effective reduction on vertical acceleration,it is suitable for the value of damping to be taken 100-200kN·s/m.The surface vibration caused by the subway train operation is mainly vertical vibration,with the increase of the distance from the middle line of the tunnel,the ground vibration trends to decrease in general,but existence a vibration strengthening area at the distance of 15m-30 m.The surface vibration decreases with the decrease of steel spring stiffness and damping,decreases with the increase of the depth of the tunnel and the density of the floating slab.It is suggested that all parameters and economic factors should be considered in the design of floating slab track so as to achieve good damping effect.