A fractional elasto-viscoplastic model for describing creep behavior of soft soil

Abstract

In order to solve the analytical solution of the general rate-dependent model and make the theoretical model better reflect the creep behavior of soil, the fractional calculus theory is applied to the EVP (elastic–viscoplastic) model based on the overstress theory. A fractional strain rate model is proposed to construct a constitutive equation of fractional strain rate. The analytical solution of the fractional creep model is solved by applying Laplace integral transformation, and the fractional creep equation under undrained conditions is discussed. Then, the undrained shear creep test results of isotropic consolidated Fukakusa clay and K0 consolidated Sackville clay are used to verify the validity of the time-based fractional creep equation and the sensitivity analysis of the analytical solution. The effectiveness of the fractional creep model for predicting the creep behavior of soil such as soft clay is revealed. The results show that the fractional EVP creep model is obviously better than the traditional integer EVP model. Moreover, when the fractional order is 1, the fractional strain rate model can be reduced to an integer strain rate model, but the fractional creep equation degenerates into a linear creep equation.