Coarse Grained Soil Constitutive Model Based On Disturbed State Concept And Parameters Determination

The disturbed state concept (DSC) is based on the idea that a deforming material element can be treated as a mixture of two reference states: relative intact (RI) state and fully adjusted (FA) state. The overall response of the soil material, i.e. the observed response, is related to the responses at the reference states through a disturbance function, which provides a coupling and interpolation mechanism between the responses of the material in the RI and FA states. During the deformation process of the soil material, the part of the material in the FA state increases, and the part in the RI state decreases. The transformation of material state from RI to FA is defined by the disturbance function D. The behavior of the material in the RI state can be simulated by a theory based on continuum mechanics, such as non-linear elasticity or elastoplasticity. The FA state refers to the asymptotic state to which the material tends to in the ultimate stages of breakage and can be simulated by critical state model.In this thesis, the author makes deeply study of the disturbed state concept, analyses and modifies Duncan-Chang E-B model corresponding to the mechanical characteristics of coarse grained soil, and proposes a DSC model based on non-linear elasticity. Expression is suggested to determine D, specific method of determining model parameters is also proposed. At last the model is verified by the comparision between the calculational stress-strain-volume change curve and the experimental data under different confined stresses. The results show that the model can describe the basic characteristics of the soil body, such as strain softening, dilatancy and it can be used on progressive failure analysis in geotechnical engineering.In the last part of thesis, a DSC model based on elastoplasticity is proposed, in which the relative intact (RI) behavior is characterized by the hierarchical single surface δ₁ model. Expression is suggested to determine the relationship between total breakage B_t and disturbance function D, which makes it possible use particle breakage to describe impairment. Establish constitutive integral procedure and verify the validity of the model.