A state-dependent hyperelastic-plastic constitutive model considering shear-induced particle breakage in granular soils

An elastic-plastic constitutive model considering particle breakage for simulation of crushable granular soils behavior is proposed. In the model, elastic strain rates are derived from a modified Helmholtz free energy function, and the influence of plastic shear work-induced particle breakage on the elastic properties of sand is taken into account as an elastic-plastic coupling mechanism. A stress ratio-driven mechanism is employed for calculation of the plastic strain rates. The proposed model is capable of tracking the evolution of the grain size distribution (GSD) due to shear-induced particle breakage. The evolving breakage index of Einav (2007) (J Mech Phys Solids 55(6):1274-1297, 2007) is interrelated to the plastic shear work to avoid overestimation of shear-induced particle breakage in loose sands. A direct comparison between the model simulations and laboratory data has been carried out for five series of drained/undrained monotonic and cyclic triaxial tests covering a wide range of initial states. For the sake of comparison, predicted behaviors from a hypoplastic constitutive model specially developed for crushable granular soils are also included. It is shown that the proposed constitutive model can provide reasonable predictions using a single set of parameters for each series of the laboratory data.