Abstract
A stress-strain-dilatancy model for sand that centers on the idea of integral modelling over the relevant density and normal stress states is presented. The model is built within the framework of the state concept, in which a relative initial state with respect to some reference states of sand (critical or steady state ; quasi steady state) is used for characterization of sand behaviour. The state index Is, which is a direct measure for the relative initial state, is used to quantify the combined influence of the density and normal stress on the stress-strain curve. Results of a series of drained p-constant torsional tests on sand samples with various initial states were used to examine and establish a rational relationship between the stress-strain parameters and the state index. It is demonstrated that there is a clear link between the relative initial state (the state index Is) and the normalized p-constant stress-strain curve of sand, and that there exists a linear correlation between Is and the parameters of a modified hyperbolic stress-strain relation. These stress-strain parameters are shown to accurately simulate sand behaviour over a wide range of densities and confining stresses. The implication of the state index as a current variable is illustrated in the case of monotonic undrained loading. Characteristic features of the model with respect to the combined influence of density and mean normal stress are discussed through a comparison with conventional sand modelling.
