A constitutive model for crushable sands involving compression and shear induced particle breakage

Properly modelling the particle breakage characteristics is important for crushable soils such as carbonate sands, rockfills and rail ballasts. According to the generation mechanism, particle breakage was decomposed into two parts: compression-induced particle breakage associated with the increase of mean effective stress and shear-induced particle breakage related to the change of shear stress ratio. The accumulation rate of the compression-induced particle breakage can be well correlated to the current stress state; while the accumulative rate of the shear-induced particle breakage depends on both the current stress state and the accumulated amount of particle breakage during past loading histories. Within the framework of the critical state plasticity, a double yield surfaces constitutive model incorporating the two particle breakage components was developed. By employing a breakage critical state surface with particle breakage being an extra dimension, the effect of particle breakage on the critical state, dilatancy, strength and modulus were involved. The drained and undrained triaxial test results of two carbonate sands and one silica sand of different densities were selected to validate the proposed model. It was shown that the proposed model is capable to reproduce well the stress-strain behavior of the crushable soils.