State-dependent constitutive model and numerical solution of self-weight consolidation

A new constitutive model is developed for the compressibility behaviour of soft clay sediments at low effective stress level. Central to this model is the realisation that at low effective stress levels the void ratio - effective stress paths of soil elements are non-unique, and dependent very much on their state. Beyond a threshold stress level, these relationships become unique. These observations have been used to develop a state-dependent constitutive model for the compressibility behaviour of soft sediments. Methods to obtain the input parameters of the model are discussed. The proposed model is used to solve finite-strain one-dimensional consolidation with pertinent initial and boundary conditions. The analyses performed using a finite difference computer code predict better the observed phenomena associated with self-weight consolidation, especially during its early stages. The comparison of the predictions shows that the present model can capture the decrease in void ratio patterns, as observed in experiments at low effective stresses, and which cannot be modelled using existing constitutive relationships.