冻土在高应力水平下通常会表现出加速蠕变特性。经典西原（Nishihara）模型可以反映衰减蠕变和稳态蠕变，但不适用于描述加速蠕变。通过对Nishihara模型中黏性元件进行修正，将黏弹性元件中的定常的黏滞系数修正为时间的函数，并在黏塑性元件中采用非定常、非牛顿黏性元件，得到的蠕变柔量可以考虑应力水平和时间的影响，使其能够反映其加速蠕变的过程。用提出的模型分别对一维和三维应力、不同应力水平下的冻土蠕变试验数据进行了拟合，拟合结果能够反映冻土从衰减蠕变和稳定蠕变状态进入加速蠕变的过程，说明了该模型对于描述冻土在不同应力下不同蠕变状态的适用性。

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.