Time-Dependent Creep Damage Model of Frozen Soil with Unsteady Fractional Order under Temperature and Stress Coupling

In order to study the creep characteristics of frozen soil under different confining pressures, triaxial creep tests of frozen soil under different temperatures are carried out and the creep deformation law of frozen soil under different confining pressures and different freezing temperatures is analyzed. In this paper, the unsteady Abel dashpot is constructed by the unsteady viscosity coefficient. On this basis, the fractional order of the viscosity dashpot is unsteady. Then, a time-dependent creep constitutive model for frozen soil based on the unsteady fractional order is established. The model can better describe the law of accelerated creep deformation of rock. Through the Levenberg–Marquardt algorithm, the parameters of the triaxial creep model are identified to verify the correctness of the creep model. The results show that the model can describe the creep deformation of frozen soil well and overcome the shortcoming that the traditional model cannot describe the law of accelerated deformation. At the same time, the agreement between the model curve and the test curve is also much greater than that between the traditional Nishihara model curve and the test curve. This lays the foundation for the later use of the creep model to simulate the settlement and horizontal displacement of subgrade soil under long-term loads and also provides a theoretical basis for the construction of other roadbed projects.