One dimensional formulae for time-dependent compression characteristics of over-consolidated clays

The time-dependent compression characteristics of clay exhibit apparent differences when loaded from the over-consolidated and normally consolidated states. Based on the Nishihara model, this paper presents one dimensional isotache-based formulae for over-consolidated clays which consists of elastic, visco-elastic and visco-plastic deformation components. The newly constructed constitutive model is used to interpret the visco-elastoplastic compression characteristics of over-consolidated clays and incorporates effects including long-term compression, strain rate dependency and stress relaxation. Corresponding analytical solutions are obtained and the methodology to determine the model parameters is then introduced. New data from a series of oedometer, constant rate of strain (CRS) tests and stress relaxation tests on piston samples of marine, lightly over-consolidated, carbonate clay from the Australian North West Shelf (NWS) are presented. These test data are used to verify the predictive capability of the proposed constitutive model, reasonable agreements between the computing and experimental results were found.