Experimental investigation and constitutive modeling of the shear creep behavior of an overconsolidated soft clay

This paper presents the results of shear creep experimental investigations carried out on Huzhou overconsolidated soft clay and subsequently proposes a constitutive model that is able to reproduce the shear creep characteristics under complex stress conditions. First, shear creep characteristics are obtained based on the analysis of results from drained triaxial shear creep tests conducted on clay samples. Then, the Yin-Graham equivalent time is extended into shear stress states; thus, the concept of shear equivalent time is formulated. Using the shear creep characteristics observed from experiments and the shear equivalent time concept, a shear stress-strain-strain rate creep model reflecting a complex loading history and loading path is proposed. Finally, the model is solved numerically with the fourth-order Runge-Kutta method, and the predictions are compared with the measured values. The results show that (1) the shear creep coefficient of Huzhou overconsolidated soft clay varies with the overconsolidation ratio levels, and there is a good correspondence between them, which is similar to the relationship of the volumetric creep coefficient and overconsolidation ratio; (2) the predicted curves of the new model are in good agreement with measured curves, which demonstrates that the model can well simulate the shear creep characteristics of soft clay under complex stress conditions.