Abstract: Soft soil is one type of material with nonlinear rheological behavior. The existing rheological models ignore nonlinear deformation under transient loading conditions. Rheological testing parameters for soft soil are mathematical parameters rather than physical model parameters. One soil generally corresponds to only one type of material parameters. But model parameters of the existing rheological model often change irregularly under varying loading conditions. Soft soils containing organic materials as the rheological phase are tested under one-dimensional consolidation-creep condition. A rheological model containing seven components is developed with same material parameters under different loading conditions. Non-linear spring is applied to describe elastic-plastic deformation subjected to transient loading. Parallel three-element components are applied to describe viscosity, plasticity and elastic deformation with time. The results show that the rheological behavior of soft soil can be accurately reflected by seven-components rheological model with incorporating cubic nonlinear transient elastic modulus.

Key words: instantaneous deformation, instantaneous elastic modulus, rheological model, model parameter