Study On The Influence Of Uneven Settlement Of High Speed Railway Subgrade On Mechanical Properties Of Vehicle-Track System

The comfort and safety of high-speed railway operation mainly depend on the high smoothness between wheels and rails and the high stability of mutual dynamic interaction.A stable roadbed structure is a prerequisite for achieving this goal.Under the combined effects of cyclic loads,groundwater,and environmental factors,the uneven settlement of the subgrade will inevitably occur.The uneven settlement of the subgrade will cause the deformation of the high-speed railway track structure and generate additional additional stress.The deformation of the track structure will be mapped to the surface of the rail,causing irregularities on the surface of the rail,which will affect the safety,smoothness and comfort of high-speed trains.Therefore,it is of great significance to study the uneven settlement of high-speed railway subgrade.In this paper,the settlement of the ballastless track subgrade of high-speed railway is taken as the research object.Based on the Winkel elastic foundation coupling beam theory and finite element method,a finite element model of slab ballastless track beam-body space is established.Fully consider the non-linear characteristics of contact between ballastless tracks,analyze the mapping relationship between the uneven settlement of the foundation under the track's own weight and the dynamic load of the train,and the irregularity of the ballastless rails.Based on this,evaluation and analysis of existing safety limits for uneven settlement of subgrade of ballastless track line on high-speed railway.The research results show that when uneven settlement of the high-speed railway line foundation occurs,the ballastless track structure will be affected by the deadweight load and the dynamic load of the train,and the follow-up settlement deformation will occur.The amplitude of the follower settlement of the ballastless track structure closer to the foundation settlement is closer to the actual settlement amplitude.The larger the amplitude of the foundation settlement,the more obvious the irregularity of the rail surface.Under the condition of 20 m settlement wavelength,when the settlement amplitude exceeds 25 mm,it is easy to form voids between the track structure and the roadbed.Under the condition of settlement amplitude,when the settlement wavelength exceeds 25 m,the void phenomenon between the subgrade and the track structure is obviously alleviated.At this time,the unevenness of the track surface can basically be consistent with the deformation of the subgrade.Based on the vehicle-track coupling system dynamics theory,a dynamic physical model of the vehicle-ballastless track-subgrade vertical coupling system is established.At the same time,the contact status between layers and the contact relationship between wheels and rails must be considered.Dynamic characteristics of high-speed vehicles caused by changes in parameters such as wavelength and amplitude,and uneven settlement of the roadbed are analyzed.The research results show that the dynamic response of the vehicle system increases with the increase of the speed of the high-speed train and increases with the amplitude of the uneven settlement of the roadbed.When the speed of the high-speed train exceeds 85km/h,it is safe for the vehicle Both the ride quality and ride comfort have a certain impact.And the uneven settlement amplitude of the 30 mm subgrade is a sensitive amplitude that causes the vehicle dynamic response.The impact of the uneven settlement wavelength of the subgrade on the vehicle dynamic characteristics increases first and then decreases.The change law,in which the vehicle system dynamic response shows a peak in the 20-30 m wavelength range.