Although the constant rate of displacement (CRD) consolidation test has been standardized for decades, its broader application remains limited because the appropriate displacement rate cannot be determined a priori for soils with unknown properties. Following the ASTM [3] recommended method for selecting the displacement rate based on the pore pressure coefficient, this study defines the characteristic displacement rate, rd,9%, as the appropriate rate corresponding to an average pore-pressure coefficient of 9%. A generalized nonlinear large-deformation numerical model is developed by solving a normalized governing equation with known moving boundary conditions using an implicit finite difference scheme. The scheme incorporates an adaptive mesh deformation technique to eliminate the convective term in the material time derivative. Based on this model, the effects of final strain, the ratio of compression index to the permeability index, the virgin compression ratio, the initial effective stress, the initial specimen height, and the initial hydraulic conductivity on the relationship between the displacement rate and the pore pressure coefficient are analyzed. A fitted formula independent of soil properties is then established between the two variables. This enables the determination of an appropriate displacement rate from a single CRD test conducted at any arbitrary rate without requiring additional incremental loading (IL) tests. CRD consolidation tests conducted at different rates are used to validate the proposed formula, and the results show good agreement with the model predictions.
