The stress-strain behaviour of calcareous sands is significantly affected by particle breakage, which leads to the impairment of dilatancy, resulting in a predominant contractive response of the soil specimen. However, only a few constitutive models consider the effects of particle fragmentation and the evolution of grain size distribution on the critical state. This study presents an extension to the deviatoric isotropic hardening model to incorporate the effects of particle breakage in crushable granular media. Furthermore, it adopts an energy-consistent elastic formulation, with stiffness moduli expressed as functions of both mean effective stress (p') and deviatoric stress (q). Based on the framework of critical state soil mechanics and multisurface plasticity, our present formulation accounts for the material state dependency [4], accurate modelling of soil dilatancy and plastic strain evolution, strain hardening as well as softening response, along with non-associativity (f ≠ g). The model requires some parameters which can be easily calibrated from conventional triaxial element tests to predict the influence of crushing under static loading. It is validated using experimental results from drained triaxial tests of coral sands conducted at different initial relative densities and confining pressures. The material model is further employed to simulate the cylindrical cavity expansion problem that finds widespread applications in borehole instabilities associated with reservoir geomechanics and petrophysics problems. Our numerical results indicate a distinctive crushing zone, in addition to the elastic and purely plastic regions predicted by the conventional elastoplastic material models. This demonstrates the model’s capability in accurately capturing the breakage characteristics of crushable granular media.