Influence Of Subgrade Differential Settlement On Running Safety Of Train And Dynamic Performance Of Track

Subgrade is the most uncontrollable part in railway engineering.The excessive differential settlement will directly threaten the safety of the train,limit the running speed of the train,reduce the passengers' comfort and accelerate the degradation of the rail.So,it has always been a very notable problem in the operation of the high-speed railway.As a traditional form of track structure,the ballast track is still widely used in high-speed railways due to good wheel/rail contact,good elastoplasticity,low cost,convenient replacement and maintenance as well as good noise absorption characteristics under the condition of certain repair maintenance,both in China and abroad.In this paper,for a detailed characterization of the differential settlement's influence,based on the theory of vehicle-track coupling dynamics,we used ABAQUS finite element analysis software to establish the train-ballast track-subgrade finite element model,analyzed the vertical dynamic responses of train track system,and obtained the differential settlement's limit by comparing them with those from the specification.Main contents and conclusions are as follows:(1)Introduced the relevant theories and methods used in establishing train-ballast track-subgrade coupling system model,infinite element,damping,dynamic analysis of ABAQUS,and the Python language in detail.(2)Introduced the establishing process of two dimensional train-ballast track-subgrade finite-infinite element model,described the selection of element and calculation parameters,the simulation of the track irregularities,and also introduced the simulation and concrete method of differential settlement curve.Finally,the correctness of the numerical model by two examples is verified.(3)Calculated the maximum of train's load reduction rate,car body's vertical acceleration,power coefficient,and the track structure's deformation corresponding to subsidence center point under the differential settlement with 100 kinds' different amplitudes and the lengths for the soft,hard soil subgrade,and got the threshold curves by comparing the results in this paper with the corresponding specification limits.Finally,we chose a typical differential settlement curve,analyzed the influence of train speed's on the limit by calculating the maximum of these dynamics indicators above.(4)Compared the maximum of car body's vertical acceleration and wheel/rail contact force respectively by means of the two dimensional and three dimensional model under two working conditions.The applicability of two-dimensional model is verified when studying the related issues about differential settlement.