CT measurement of damage characteristics of meso-structure of freeze-thawed granite in cold regions and preliminary exploration of its mechanical behavior during a single freeze-thaw process

The freeze-thaw (FT) damage characteristics of granite after different FT cycles were studied using computed tomography (CT) images. The three-dimensional (3D) volume numbers in the image were extracted to obtain the 3D pore structure of representative volume elements (RVEs) of granite under different FT cycles. The CT images of granite after 80 FT cycles were selected to draw reference lines for quantitative analysis of the distribution of meso-cracks in granite after FT cycles. Subsequently, a finite element model was established to explore the mechanical properties of minerals in granite during a single FT process. The results show that the FT damage inside the granite exhibits fracture characteristics, and the number of internal cracks, cracks area, and voxel porosity increase with the increase of FT cycles. After 80 FT cycles, the distribution of meso-cracks on the cross-section of granite exhibits significant anisotropy, and the distribution density and variation coefficient of meso-cracks vary with the dip direction angle of the reference line. The maximum principal stress and strain in the finite element model are negatively related to temperature. The maximum principal stress and strain of biotite minerals are consistently higher than those of feldspar and mica during FT cycles. The results can provide a reference for exploring the internal mechanism of the weakening of mechanical properties of granite microstructure caused by FT damage in cold regions.