Experimental and numerical investigation on the mechanical response and fracture mechanism of hollow granite under conventional triaxial compression

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Abstract The deformation, strength and crack damage of granite specimens with different aperture diameters were investigated by triaxial compression tests. The fracture characteristic and failure mechanism inside the hollow granite were explored with the help of a reconstruction method for cracks based on CT scanning and the three-dimensional grain-based model (GBM3D). The experimental results show that the Poisson’s ratio of the hollow granite specimens under triaxial compression is smaller than that of intact specimens and decreases gradually with the increase of aperture diameter. The effect of aperture diameter on Young’s modulus is larger under lower confining pressure, and will be weakened as confining pressure increases. The hollow granite at different confining pressures has four typical stress-volumetric strain curves. Its uniaxial strength and crack damage threshold gradually decrease as the aperture diameter increases, as does the gap between the crack damage threshold and the peak strength. Their ratio gradually increases and tends to one as confining pressure increases. In the triaxial compression tests, the compressive strength of hollow granites increases with the increase of confining pressure, but decreases approximately linearly with the increase of aperture diameter, and its sensitivity to diameter is higher under high confining pressures. The failure mode of granite fails with a complex network of axial fractures under uniaxial compression, while is dominated by shear fracture under triaxial compression. Under confining pressure, the increase in aperture diameter leads to a greater concentration of cracks at the end of the specimen and more severe spalling at the inner diameter wall. Article Highlights (1) Conduct a series of triaxial experiments and numerical simulation for hollow granite with various hole diameters. (2) Analyze the eff ect of hole diameter and σ3 on deformation parameters of hollow granite under conventionaltriaxial compression. (3) Investigate the eff ect of hole diameter and σ3 on peak strength and crack damage threshold of hollow granite. (4) Explore the damage failure mechanism of hollow granite by 3D X-ray micro-CT and GBM3D simulation.

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