Research On Enviromental Vibration Caused By The Underground Train Base On Vehicle-Track-Tunel Coupling

With the continuous improvement of the urbanization level,the underground train is an effective way to solve the urban road traffic congestion.However,the vibration generated in the process of the underground train running is transmitted to the ground through the track,tunnel and soil,causing environmental vibration.This affects people’s normal life and work.Based on the research of scholars at home and abroad,this paper will analyze the influencing factors of environmental vibration caused by the underground train.Vehicle-track coupling dynamics will be used to provide excitation sources for environmental vibration analysis.The vehicle-track-tunnel coupling system is solved by the whole-process iterative method.The influence of different factors on environmental vibration caused by the underground train is analyzed.The specific research contents are as follows:On the basis of vehicle-track coupling dynamics,a track finite element suitable for vehicle-track-tunnel coupling is proposed.The differential equations of vehicle and track dynamics were established,and were coupled by Hertz contact.In this paper,a new explicit integration method is used as the predictive force in the integral time step,and Newmark method,iterative process and relaxation factor are combined to solve the vehicle-track coupling dynamic equation.The rationality and validity of the calculated results were verified by comparing with the results in the literature,and the selection of integral step size and relaxation factor were analyzed.The rationality and effectiveness of the proposed method were verified by comparing with the results of literatures.The choice of integration step size and the choice of relaxation factor are analyzed.The results show that the relaxation factor can maintain the numerical stability of the proposed method.The maximum integration step size of the method in this paper is 0.0005 s,and the relaxation factor is 0.1.The vehicle-track coupling dynamic model was used as the excitation source to establish the vehicle-track-tunnel coupling vibration system.The whole system is divided into two sub-models,vehicle-track and tunnel.The coupling relationship between the sub-models is taken as displacement coordination and force balance.The improved inter-system iteration method is used to solve the two subsystems.Based on the characteristics of the improved inter-system iteration method,the commercial finite element software is used to model the tunnel,and the data interaction between the vehicle-track sub-model and the tunnel sub-model is realized.The rationality and effectiveness of the vehicletrack-tunnel coupling vibration system are verified by comparing the calculation results in the literature.The responses of vehicle-rail systems in coupled tunnel and uncoupled tunnel are compared.The variation law of vibration response peak value in the iterative process is analyzed.The results show that the influence of tunnel settlement on vehicle and track displacement can be considered after coupling the tunnel.The speed and acceleration of the vehicle and track tend to be roughly the same in both cases.Combined with the literature process iteration method in railway bridge in the calculation of coupling and the coupling of the railway tunnel can satisfy convergence.Based on the Vehicle-track-tunnel coupling vibration system,the stiffness of rail coupler,damping of rail coupler and buried depth of tunnel were selected as the three factors of environmental vibration.The ground above the vibration source was selected as the pickup point of acceleration,and Z-vibration level was used as the evaluation index of environmental vibration.Firstly,single factor analysis was carried out to determine the influence of each factor on environmental vibration.Finally,multi-factor analysis was carried out by orthogonal test method to determine the significance of the influence of three factors on environmental vibration.The results show that the significance of the impact on environmental vibration is in the order of tunnel buried depth,rail coupler damping and rail coupler stiffness.The environmental vibration decreases with the increase of the buried depth of the tunnel and the damping of the rail coupler.For the rail coupler,the environmental vibration decreases with the increase of rigidity from 40 k N/mm to 60 k N/mm,and increases with the increase of rigidity from 60 k N/mm to 90 k N/mm.