在季冻区高等级公路路基场地取土，制成重塑土试件进行冻融循环试验。而后对经历不同冻融循环次数的土体进行三轴固结排水（CD）剪切试验，测得应力、应变数据。在大量试验数据的基础上，遵循岩土本构变化规律，以岩土弹塑性力学为理论基础，在p-q空间，以椭圆方程拟合体变屈服面，以抛物线方程拟合剪切屈服面，采用塑性关联流动，得到考虑冻融循环条件下融土的弹塑性本构方程。通过编程计算后，对比计算与试验结果，证明该双屈服面本构模型能够较为准确地预估冻融循环土体的应力-应变关系，该本构模型对季冻区路基土体长期稳定性分析和工程预测具有重要参考意义。

The freeze-thaw cycle tests were conducted on the remoulded soil samples taken from a highway subgrade in a seasonally frozen area. The triaxial compression tests under the consolidated-drained condition were carried out on the remoulded samples subjected to freeze-thaw cycle, and stress-strain data were obtained. Based on the experimental results and the theory of elasto- plasticity, an elliptic equation is proposed to fit the yield surface in the p-q coordinate system, while a parabolic equation is proposed to fit shear yield surface, from which an elastic-plastic constitutive equation was developed following an associated flow rule with considering freeze-thaw cycles. By comparing the theoretical calculation with the experimental data, it is shown that the proposed double-yield surface constitutive model can accurately predict the frozen soil stress-strain relationship. The model provides a theoretical basis for long-term stability analysis and engineering prediction of subgrade soil in seasonally frozen areas.