Constitutive Modelling of the Deformation and Degradation of Railway Ballast Using Multi-laminate Framework

Coarse granular materials such as railway ballast used in the shallow layers of railway tracks are often subjected to moving loads, which cause complex stress conditions involving the rotation of principal stress axes. Further, these materials are involved with particle breakage, which is also affected by the stress changes in the track. Computer modelling incorporating constitutive relationships is an effective technique for assessing the deformation behaviour of coarse granular materials under such conditions. This paper presents a constitutive model for coarse granular materials in multilaminate framework, considering classical plasticity and critical state concepts. A criterion for particle breakage in multi-laminate framework and its effect on the stress-strain behaviour has been incorporated using constitutive relationships in multilaminate framework. The influence of minor principal stress and principal stress rotation on the stress-strain, volumetric strain and particle breakage of these materials have been discussed.