Ballast deformation and degradation in railway tracks are the key factors affecting track performance and frequent track maintenance. With the introduction of high-speed and heavy haul trains, it is very important to understand their influence on ballast performance, especially when increasing train speeds are associated with dynamic stress amplification and principal stress rotation. This paper discusses a constitutive model that can be used to predict the permanent strains as well as particle breakage of ballast, using Ballast Breakage Index (BBI) capturing principal stress rotation. The constitutive model is based on a multi-laminate framework, where constitutive relationships were developed at a set of integration planes representing inter-particle contact planes using bounding surface plasticity. The model after calibration with large-scale cyclic triaxial testing data, is used to predict the deformation and degradation response of ballast under dynamic conditions with and without principal stress rotation. The outcomes of this model showed higher deformations and breakage under stress state with principal stress rotation when compared to a triaxial stress state. Empirical relationships are proposed that correlate the permanent strains and breakage at shakedown using an equivalent cyclic stress ratio combining the effects of vertical and shear stresses.