Research On Dynamic Response Characteristics Of Subgrade-bridge Transition Region Of Heavy-haul Railway Under Roller Excitation

Heavy-haul railway puts forward a higher demand in the dynamic performance of subgrade filler due to its technical characteristics of heavy train axle load and large traction quality.Especially for the transition section between subgrade and bridge,selecting appropriate subgrade filler and transition form can ensure the smooth operation and driving safety of train.In this dissertation,taking the vibratory roller during the construction stage as the excitation source,the field test is carried out to obtain the measured information of dynamic stress,vibration acceleration and vibration displacement in the transition region(subgrade and transition section)of heavy-haul railway.Combined with numerical analysis,the distribution law of dynamic response in the transition region along the longitudinal direction of the line and subgrade depth is studied,and the effects of different subgrade fillers,driving speed,excitation force and driving direction on dynamic response are analyzed.The main research work and results of this dissertation are as follows:(1)The dynamic response test scheme of subgrade-bridge transition region under the roller excitation was prepared according to the actual excitation test situation.The field test selected the typical test section to embed the test elements,and the vibration signals of dynamic stress,vibration acceleration and vibration displacement of the transition subgrade were obtained under 10 different working conditions of different driving speeds,exciting force and driving directions.The vibration test signals were corrected by eliminating the trend term and five-point smoothing method.(2)The time domain analysis of the dynamic response of the transition region under different test sections and different working conditions is carried out,and the distribution laws of the dynamic response of the transition region along the longitudinal direction of the line and the depth of the subgrade under different excitation forces,different driving speeds and different driving directions are obtained.(3)The frequency domain analysis of vibration acceleration in the transition region under different depths and working conditions is carried out,and the vibration acceleration is decomposed into five frequency bands by wavelet analysis.The effects of different subgrade filler,driving speed,exciting force and driving direction on the total vibration energy and the distribution of vibration energy in each frequency band are discussed.(4)The three-dimensional dynamic infinite element boundary numerical model of vibration wheel transition region coupling is established.The simple harmonic load and discrete pulse are used to simulate the vibration load of roller respectively.The calculated dynamic stress and vibration acceleration are compared with the measured values.The results show that the calculated results of simple harmonic load model are closer to the measured values.(5)Using the verified numerical model and calculation parameters,the transition effect evaluation indexes such as the depth of subgrade working area in the transition section,equivalent stiffness and the contact force between vibratory wheel and subgrade surface are calculated and analyzed,and the transition effects of different transition subgrade fillers are evaluated.