Experimental study of the frozen soil–structure interface shear strength deterioration mechanism during thawing

In cold regions, an increase in temperature deteriorates the performance of frozen soil–structure interfaces and damages structures. Unfrozen water content, imaged using nuclear magnetic resonance, and interface shear tests under normal pressures were used to determine the shear failure features and damage degradation mechanism of frozen soil–structure interfaces during thawing. Variations in the unfrozen water content at the frozen soil–structure interface and the progressive deterioration of the shear strength of the interface were observed for samples that thaw at different temperatures. Results revealed that the decrease in the shear strength during the thawing process was closely related to the presence of unfrozen water content (ice) in the vicinity of the frozen soil–structure interface. The shear strength of the interface was decreased considerably affected when the amount of unfrozen water increased during thawing (i.e., the amount of ice decreased), with the loss rate reaching 80.01%. The increased unfrozen water content around the interface changed the stress path of the frozen soil–structure interface and melted the ice within the macropores of the interface during thawing, thus causing the rupture of ice to disappear; moreover, the stress–strain relation of the interface caused it to gradually transform into a hardened structure.