Abstract
This paper reviewed some salient features evolving through mathematical and numerical modelling of ballasted track components incorporating recycled rubber products. Firstly, a constitutive model based on the bounding surface concept was introduced to simulate the shear stress-strain response of waste mixtures (i.e., recycled rubber crumbs, coal wash, and steel furnace slag) used for the capping layer placed below the ballast medium, whereby the energy absorbing property resulting from the inclusion of different amounts of rubber has been captured. Subsequently, key research findings concerning the inclusion of recycled rubber mats on ballasted tracks for reduced particle degradation under cyclic loading were examined and discussed. Discrete element modelling (DEM) coupled with Finite element modelling (FEM) to micro-mechanically characterise ballast behaviour with and without rubber mats offers invaluable insight into real-life track operations. In particular, this coupled DEM-FEM model facilitates the exploration of micromechanical aspects of particle breakage, contact force distributions within the granular assembly, and the orientation of contacts during cyclic loading.
Highlights
This paper described mathematical and numerical approaches to investigate the improved performance of track substructure layers incorporating geo-inclusions
Blends [27], as well as Steel furnace slag (SFS)+coal wash (CW) blends tested by Tasalloti et al [40] and sand-rubber crumbs (RC) blends examined by Youwai and Bergado [26]
The pioneering work appropriate for soil-rubber mixtures with larger particles of rubber, such as chips or tyre in applying the Discrete element modelling (DEM) to simulate ballast was conducted by McDowell and Bolton [64] at fibre because they may not reach a critical state even after large axial strain (>25%) due the Cambridge University; it continued with researchers at Nottingham University to the continuous deformation experienced by larger rubber particles towards the end of
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Coupled discrete-continuum modelling was used to examine the cyclic loading behaviour of a track specimen and the role of rubber mats in reducing ballast degradation These mathematical and numerical models were calibrated and validated based on extensive laboratory testing. The effect of the RC content on the critical state response is investigated, and the total work input is considered to be related to the critical state parameters to capture the energy absorbing characteristics due to adding rubber In this context, a constitutive model following the bounding surface theory and the critical state concept is developed for the waste mixtures. The proposed model was verified by comparing the prediction results with the laboratory data for SFS+CW+RC blends [27], as well as SFS+CW blends tested by Tasalloti et al [40] and sand-RC blends examined by Youwai and Bergado [26]
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