Feasibility Study On Prediction Of Fixed Point Excitation Of Railway Vibration

With the promulgation and implementation of the "National Comprehensive Three-dimensional Transportation Network Planning Outline" and the continuous development of the urbanization process,Intercity railways,high-speed railways and urban rail transit are bound to be more closely linked in the future.At the same time,the impact of train operation on the surrounding environment will attract more and more attention.The current prediction and evaluation of the environmental vibration response of rail transit is only at the beginning of the engineering design and construction,and the empirical prediction formula is used to predict the vibration along the line,but its prediction accuracy is greatly affected by complex factors such as geological conditions,rail transit systems,and infrastructure,it is difficult to predict accurately.Regarding the inaccuracy of the existing empirical prediction formulas in the environmental vibration prediction of rail transit,which caused the vibration and noise to exceed the environmental impact assessment standards after line operation,this paper proposes a "fixed-point excitation prediction method" based on actual measurement,it can meet the demand for high-precision vibration prediction of key vibration targets.In this dissertation,a vehicle-track interaction simulation vibration excitation device"suitable for different lines is designed.The requirement for this device is to be able to simulate the actual effect of the train’s dynamic load.Therefore,the accuracy of the train dynamic load simulation function is analyzed,and the fixed-point excitation vibration source function model is derived;based on this model,a "tunnel-foundation" finite element model suitable for high-speed railways and a "track-foundation"finite element model suitable for subways are established,and the application of the fixed-point vibration prediction method in high-speed railway and subway is studied.The main results of the thesis are as follows:(1)When loading with the fitted value of the train dynamic load simulation function,the change trend of the vibration response in the surrounding environment of the line is basically the same as the actual train operation.The high frequency part of the train vibration increases with the distance from the track centerline.Fast attenuation,the vibration energy at the ground measurement points is concentrated within 0～30Hz.(2)Theoretical derivation has obtained a fixed-point excitation vibration source function model that is convenient for loading.This model can accurately simulate each component of the train’s dynamic load.When the fixed-point excitation method is used to load,the vibration response of the sensitive point is consistent with the actual train operation.The response at this point is similar.(3)Calculations show that under certain high-speed railway conditions,the vibration response prediction results of sensitive points obtained by the fixed-point vibration prediction method are slightly larger than the numerical simulation results,with a relative error of 4.7%,which is compared with the empirical formula method(relative error of 16.6%)The accuracy is greatly improved.(4)Calculations show that under certain subway conditions,the prediction result of the sensitive point vibration response obtained by the fixed-point excitation prediction method is slightly larger than the numerical simulation result,with a relative error of 5.5%,which is compared with the empirical formula method(relative error of 26.1%)The accuracy is greatly improved.Compared with the empirical prediction formula,the fixed-point vibration prediction method has higher accuracy when applied to the environmental vibration prediction of rail transit,and has a broad market prospect.