Study On Dynamic Response Of Ballastless Track Box Subgrade Of High-speed Railway

In just 30 years,China has achieved remarkable achievements in high-speed transportation.However,in recent years,with the significant increase in high-speed train speed,the requirements for roadbed in the high-speed railway system have become increasingly strict.The problems exposed by traditional filling methods for roadbed are becoming increasingly serious,so it is necessary to study new types of roadbed.The box shaped roadbed structure,as a new type of concrete structure,fundamentally solves the demand for high-quality filling materials for high-speed railways in traditional filling methods,and reduces the land area occupied by the roadbed.The structure of this roadbed is significantly different from traditional roadbed,and currently there have been no scholars in China conducting analysis and research on it.This article mainly uses numerical simulation to establish single line and double line finite element models of box subgrade using ABAQUS finite element software.It explores the basic dynamic stress distribution law and dynamic displacement distribution law of single line and double line box subgrade structural models under different forms of train loads,and obtains the following conclusions:(1)This article adopts two types of train load application methods for single line static model and double line dynamic model.One is to simulate train load in the form of concentrated force,and the other is to simulate train moving load in the form of train load curve.Both loading methods can effectively simulate train load.(2)Compared with traditional roadbed,the overall dynamic displacement distribution of box shaped roadbed is more uniform;In the static model,the vertical dynamic displacement of the box shaped roadbed is only 67.8% of that of the traditional fill roadbed;In the dynamic model,the vertical dynamic displacement of the box shaped roadbed is only 80% of that of the traditional fill roadbed;(3)The maximum vertical dynamic stress of the top plate of the box shaped roadbed appears below the load position,then gradually decreases towards both sides,and undergoes a small abrupt change on the upper surface at the connection with the vertical plate,which decreases with the increase of roadbed depth;The bottom plate only experiences local stress increase at the connection position with the vertical plate,and the dynamic stress at other positions is less than 10 k Pa.(4)When dynamic stress is transmitted to the vertical plate,it decays very quickly with depth;The vertical dynamic stress of the vertical plate decreases first and then increases with increasing depth;The ratio of the increase range of vertical dynamic stress in the vertical plate to the overall height of the vertical plate,with the static model accounting for 65% and the dynamic model accounting for 30-50%;(5)The different positions and quantities of vertical plates have a significant impact on the vertical dynamic stress of the box roadbed.In the dual track dynamic model,5vertical plates are set up,and when a vertical plate is set below the center of the track plate,the train dynamic stress can be better transmitted downwards through the vertical plate,reducing the burden of train dynamic stress on the top plate.Compared to other working conditions,the reduction is 30%～47.5%.