A novel approach for characterizing frozen soil damage based on mesostructure

In this study, the relationship between the computed tomography (CT) number and the density of frozen soil was established on a macro and mesoscopic scale, aimed at overcoming the shortcomings of the mesoscopic damage behavior predicted by previous macroscopic research on frozen soil. In addition, considering the influence of stress level and temperature, a mesoscopic structural damage variable was proposed, which could reflect the damage characteristics of frozen soil. On this basis, combining the meso-damage of frozen soil with the macro-mechanical response, the mechanism of the damage evolution of frozen soil under stress was studied. It was found that the variation law of porosity was consistent with the law of the mesoscopic damage expansion in frozen soil. In the initial stage of stress loading, compaction was observed before meso-crack expansion. The internal structure exhibited a strengthening effect, by which the damage was reduced. The macroscopic mechanical properties were characterized by an elastic strain phase. As the stress continued to increase, an inflection point of the damage value appeared, and the damage gradually increased. The starting point of the meso-fracture expansion curve could represent the stress yield point on the macroscopic mechanical curve, and also represented the inflection point of the volume change of the material from the contraction to the dilatancy. When the damage value was gradually increased and became equal to the initial value, the deviatoric stress reached the peak of the macroscopic mechanical curve.