The impact of periodic freezing-thawing cycling on the stress-relaxation behavior of expansive soil, which was discovered during the construction of the Harbin-Jiamusi high-speed railway, was investigated in this paper. The laboratory tests associated with this study involved X-ray diffraction (XRD), thermal analysis, and direct shear testing. Test results indicate that shear stress decreases gradually in line with the number of freeze-thaw (F-T) cycling (N_FT). When the N_FT exceeds 7, F-T cycling no longer has any observably significant influence on the shear stress. The relaxation rate decreases during the first F-T cycle, after which almost no appreciable effect from F-T cycling is visible. It is concluded that, during the relaxation process, the shear stress decreases gradually and tends towards a stable value. A three stage process for the stress relaxation of soil samples affected by F-T cycling was observed: instantaneous relaxation; attenuated relaxation; and steady relaxation. Based on the experimental results, a disturbed state concept (DSC)-based stress-relaxation model for expansive soil exposed to freeze-thaw cycling was proposed. Close agreement between the experimental data and results predicted according to the model confirms the model’s validity.

研究了周期性冻融循环对膨胀土应力松弛行为的影响。哈尔滨至佳木斯高速铁路的施工过程中发现了膨胀松弛土的应力松弛行为。与这项研究相关的实验室测试涉及X射线衍射（XRD），热分析和直接剪切测试。测试结果表明，剪切应力随着冻融（FT）循环次数（N _FT）的增加而逐渐减小。当N _FT超过7时，FT循环不再对剪切应力有任何明显的影响。松弛速率在第一个FT循环中降低，此后几乎看不到FT循环的明显影响。结论是，在松弛过程中，剪切应力逐渐减小并趋于稳定值。观察到了受FT循环影响的土壤样品应力松弛的三个阶段过程：瞬时松弛；瞬时应变；瞬时应变。衰减松弛 和稳定的放松。基于实验结果，提出了基于扰动状态概念（DSC）的膨胀土冻融循环应力松弛模型。实验数据与根据模型预测的结果之间的紧密一致性证实了模型的有效性。