Experimental and Theoretical Investigation on the Unloading Creep Behaviors of Frozen Soil

The unloading creep deformation and failure of the frozen surrounding rock and soil stratum are common problems in artificial freezing construction. This research aims to experimentally and theoretically study the unloading creep behaviors of frozen soil. A wide range of test conditions, including different pressure history, shear stress paths, and creep stress levels, were employed to examine the sensitivity of triaxial shear and creep behaviors to the selected experimental variables. The testing results manifest that both the axial deformation and the volumetric deformation behaviors are dependent on the pressure history and shear stress path at the shear stage and creep stage. The three-stage damage evolution feature during the entire creep process was experimentally observed, and the damage evolution model based on the disturbance state concept was presented to characterize this damage accumulation process. A new fractal creep model, considering the effect of pressure history and shear stress path on the rheologic behaviors, was proposed. The capability of the fractal creep model was examined by predicting the triaxial creep responses of frozen soil under different stress paths. The comparison results exhibit very good agreement between the experimental curves and the simulation responses determined from the proposed creep model.