Abstract: The prediction and control of the long-term deformation of clay is a crucial problem in the construction of a large quantity of projects. Predicting clay deformation conventionally via creep test is time-consuming, challenging in considering complex stress path, and also unsuitable for complicated finite element analysis. In this paper, the strength, deformation and rate sensitivity of saturated over-consolidated clay and artificial structural clay were obtained via triaxial shear tests under three different loading rates. On this basis, parameters of an elastic-viscoplastic constitutive model based on super-subloading surface were obtained, and the rate sensitivity and creep deformation of clay were estimated by the model. Results revealed that: 1) compared with conventional triaxial test, predicting the long-term deformation of clay in association with rate sensitivity test is highly efficient with only several shear test at different loading rates added yet no additional test conditions; 2) the parameters of the constitutive model determined by rate sensitivity test can be used to predict the creep deformation of clay correctly, and the prediction results are in good agreement with test results; 3) the elastic-viscoplastic constitutive model based on super-subloading surface can be embedded in finite element program to calculate the complex boundary value problems. In conclusion, the presented method of long-term deformation prediction of clay is of sound value in engineering application.

Key words: soil deformation, rate sensitivity, elastic-viscoplastic, constitutive model, creep, super-subloading surface