A modified creep constitutive equation for frozen soil based on Nishihara model

Frozen soil exhibits accelerated creep behavior under high stress level. Nishihara model can describe both decay and stable creeps, however it is not suitable for accelerated creep. Non-Newtonian viscous element is used in the modified Nishihara model to describe the accelerated creep behavior. The coefficient of viscosity in viscoelastic part is modified to be a function of time; and the non-Newtonian viscous element is used in viscoplastic part. The creep compliance of the modified model is a function of stress level and time; therefore, the accelerated creep behavior of frozen soil under high stress level can be considered. One-dimensional and three-dimensional creep behaviors of frozen soil under different stress levels are fitted by using the modified model. The results show that the proposed model can describe the accelerated creep behavior under high stress level after decayed creep stage and stable creep state. The proposed model is suitable for describing different kinds of creep behaviors of frozen soil under different stress conditions.