Macro-meso fracture evolution mechanism of hollow cylindrical granite with different hole diameters under conventional triaxial compression

In order to study and analyze the stability of engineering rock mass under non-uniform triaxial stress and obtain the evolution mechanism of the whole process of fracture, a series of conventional triaxial compression tests and three-dimensional numerical simulation tests were carried out on hollow granite specimens with different diameters. The bearing capacity of hollow cylindrical specimen is analyzed based on elasticity. The results show that: 1) Under low confining pressure, the tensile strain near the hole of the hollow cylindrical specimen is obvious, and the specimen deformation near the hole is significant. At the initial stage of loading, the compressive stress and compressive strain of the specimen are widely distributed. With the progress of loading, the number of microelements subjected to tensile strain gradually increases, and even spreads throughout the specimen; 2) Under conventional triaxial compression, the cracking position of hollow cylinder specimens is concentrated in the upper and lower parts, and the final fracture mode is generally compressive shear failure. The final fracture mode of complete specimen is generally tensile fracture. Under high confining pressure, the tensile cracks of the sample are concentrated in the upper and lower parts and are not connected, while the cracks of the upper and lower parts of the intact sample will expand and connect to form a fracture surface; 3) In addition, the tensile crack widths of intact and hollow cylindrical specimens under low confining pressure are larger than those under high confining pressure.