Associated Generalized Plasticity Framework for Modeling Gravelly Soils Considering Particle Breakage

Gravelly soils are used extensively for a wide range of engineering applications. One example is railway ballast, and another is the fill for rock-filled dams. These soils are usually subjected to complicated loading, including high pressure, repeated loading from trains, and earthquake loading. Depending on the natural characteristics of soil particles and the level of external loading, gravelly soils may undergo particle breakage, which modifies the strength and deformation properties of the soils. To better estimate the response of earth structures with gravelly soils, it is necessary to describe particle breakage properly, its relation with external loading, and its effect on soil properties. In this study, a generalized plasticity framework, based on critical-state soil mechanics and following the associated flow rule, was developed based on the unique responses of gravelly soils. Particle breakage and its effects were described by a translating critical-state line that was related to dissipated plastic energy through a hyperbolic function. The responses of six gravelly soils along different stress paths were simulated using the proposed model. It was shown that with 12 parameters, the constitutive model was capable of describing the responses of gravelly soils over a wide range of initial void ratios and initial confining pressures, as well as along different stress paths. The model parameters, most of which have definite physical meanings, can be calibrated through conventional triaxial compression tests. This framework will provide a basis for simulating the cyclic responses of gravelly soils.