A simple creep constitutive model for soft clays based on volumetric strain characteristics

The soft clays are widely distributed, and one of the prominent engineering problems is the creep behavior. In order to predict the creep deformation of soft clays in an easier and more acceptable way, a simple creep constitutive model has been proposed in this paper. Firstly, the triaxial creep test data indicated that, the strain-time (e-t) curve showing in the e-lgt space can be divided into two lines with different slopes, and the time referring to the demarcation point is named as tEOP. Thereafter, the strain increments occurred after the time tEOP are totally assumed to be the creep components, and the elastic and plastic strains had occurred before tEOP. A hyperbolic equation expressing the relationship between creep volumetric strain, stress and time is proposed, with several triaxial creep test data of soft clays verifying the applicability. Additionally, the creep flow law is suggested to be similar with the plastic flow law of the modified Cam-Clay model, and the proposed volumetric strain equation is used to deduced the scaling factor for creep strains. Therefore, a creep constitutive model is thereby established, and verified by successfully predicting the creep principal strains of triaxial specimens.