A Disturbed State Concept-Based Stress-Relaxation Model for Expansive Soil Exposed to Freeze-Thaw Cycling

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.