An investigation of the dynamic behaviour of track transition zones using discrete element modelling
Previous investigations have shown that an abrupt stiffness change in track support is often associated with accelerated rates of deterioration of track geometry, high maintenance demand and poor ride quality. However, at present, there is no detailed understanding of the mechanisms of the deterioration of track geometry at transition zones. This paper aims to use the discrete element method to investigate transition zones from a micromechanical perspective. A simple track transition model with dimensions 2.1 m x 0.3 m x 0.45 m was simulated by using PFC3D. In order to identify and evaluate appropriate mitigation methods, two kinds of transition patterns, including a single step change and a multi step-by-step change for subgrade stiffness distribution were tested. The influence of train direction, speed and axle load on the transition was also investigated. In addition, geogrid was used in the ballast layer to examine the effects of geogrid reinforcement. This paper provides insight into the factors that can cause or accelerate track degradation at the transition zones, in order to identify and evaluate appropriate mitigation design.